When one of the McEnroe children gets sick, they all do. The two boys and three girls share a back room measuring five yards by four - and what little air it holds. Only the flu bugs are thriving. "Colds and coughs take off like wildfire," their father, Raymond McEnroe, said yesterday. "There just isn't enough oxygen to go round."

Aged two to nine, the McEnroe children will soon be getting a little sister. And even more cramped. That, explain housing experts, is what happens in Scotland's housing trap.

The McEnroes are not poor. Raymond, 41, has a good job, managing the Glasgow wing of a successful retail letting business. They pay their rent, their nursery bills and their council tax. But they cannot get on the housing ladder, and there is nothing - at least not remotely close to their home in the east end of Glasgow - for affordable rent.

"People don't believe it when I tell them we're still in a two-bedroom rented flat," Raymond says. "It sounds Dickensian. Now, when people ask me what I do, I say I am a spaceman. All I do is try to find space. There's never enough."

Raymond and his wife Lorraine, 34, who is due to have her sixth child this weekend, share a room that doubles as a store. Clothing, toys, even bikes are neatly piled against the walls. The children are stacked up, too. Joe, their eldest, at nine, is the lucky one. He gets the top bunk to himself in their back bedroom. Craig, seven, and Rose, six, share the bottom bunk. Elizabeth, four, and Lorraine, who will be three next month, have to sleep on a mattress pulled out at bedtime.

Right now the children - all full of energy and laughs - rub along well. "But what is going to happen when they are teenagers?" says Lorraine. "All I want is an extra room so there is one for the boys and one for the girls."

The couple are on all the waiting lists for a new rented home. They'd be happy to pay more - if one of the city's social landlords could provide a home. "We're been told we don't have priority," says Raymond. "The children, apparently, are not old enough."

So how did the McEnroes find themselves in this situation? The answer lies in the oddities of Scotland's housing market. Ten years ago, when the couple started their family, houses were relatively cheap. Now, however, the average price of a home in the city is £141,000 - around five times the average income. As prices soar, more and more people are turning back to social housing.

A generation ago, around two-thirds of Scots rented, with the rest in "bought" houses. Now the situation has almost reversed. But with demand for decent, affordable social housing increasing again, the country faces a major problem. There are still pockets of more or less affordable housing in Glasgow - and across Scotland - but they are getting increasingly squeezed.

For years public landlords have been planning for a decline in demand for social housing. In Glasgow, which has always had the single biggest stock of council housing, the changes have been most dramatic. Many of the best social houses - the big kind that would have suited the McEnroes - have been snapped up by their tenants under right-to-buy legislation introduced in the early 1980s.

Wholesale regeneration, usually led by the community-based housing associations spawned at around the same time, has replaced some of the worst homes in Europe. One source, however, admits there is an awful lot to do. "We just don't have the stock to match the people we've got. We don't have enough large family homes. We don't have enough homes adapted for people with wheelchairs. We don't have enough decent homes. It's just not a good fit."

GLASGOW was the place where the last two Labour and LibDem administrations pushed through their flagship housing policy, stock transfer. The old council housing department was replaced by Glasgow Housing Association, with promises of £1.5bn in investment. Nobody has "unpromised" that investment. But even within GHA, some are now admitting the money they have might not be enough to provide all of the 3000 new homes the organisation has committed to.

Overall, there are supposed to be some 13,000 new homes put up in Glasgow by 2013 for social housing, 10,000 by the smaller community-based organisations. Things are not going well. One senior housing official said: "Progress towards this figure has been woeful - 300 units of the GHA 3000 being delivered, 600 of the reprovisioning and 2100 of mainstream. We have six years to deliver around 10,000 units, which is not looking likely." GHA, meanwhile, has massively increased its programme of demolitions, from an initial 14,000 to 19,000 without planning replacement homes.

So how big is the housing shortfall going to be in Glasgow or the rest of Scotland? Nobody seems to know for sure. Right now the private letting market has taken up much of the slack, partly thanks to the buy-to-let boom. Whole neighbourhoods are becoming private let zones.

Stephen Hurrel, a sculptor, owns a top flat in one of the sturdy but often shabby Victorian tenements in Govanhill, on Glasgow's south side, one of Scotland's most diverse communities. He's the only owner-occupier left in his close. "People come and they go away again. As soon as you get to know someone and give them a nod, they've gone."

Many of the flats in Govanhill are now packed, let by the room to recent migrants, another complication in the housing market. Others fail to meet even today's modest "tolerable standards". Overcrowding is common. Some back courts - run by the local housing association - are spotless. Others, including Mr Hurrel's, have turned into cowps.

But will the private letting market hold up under new pressures? Reforms will soon see housing benefit paid to recipients in cash. Some landlords see that making their business more risky.

There are plenty of families even worse off than the McEnroes; people who have nowhere to stay at all. Nearly 30,000 applications were made to councils under homeless legislation in the six months to September last year, a fall of 2% on the same period in the previous year. That figure is going in the right direction. Indeed, Scotland has set some of Europe's most progressive targets for homelessness, including new statutory duties for local authorities to house everyone who is not "intentionally homeless".

But councils are still struggling. There were 8626 single people and families living in temporary housing at Hogmanay, 12% more than at the end of 2005. Around 3000 of those households were families with children or included pregnant women.

Shelter, the housing and homelessness charity, is now campaigning for an extra 30,000 affordable homes to be built over the next three years. Would building more social housing hurt house prices?

"It is in nobody's interests to see house prices collapse," says Shelter's Archie Stoddart. "But it would be much better if they would just grow a bit slower. Perhaps building more affordable homes for rent might take the heat out of that market."

Soaring house prices are doing more than making it difficult for families such as the McEnroes to find space. Stoddart believes they are reinforcing fundamental inequalities. "Over time we are going to see the effects of this dramatic rise in house prices," he says. "Bluntly, it is going to increase inequality. There will be a huge difference between people who have equity and people who don't, perhaps in the way they are cared for when they are older. What if, in 20 years, there is a drug that the health service can't afford? There will be people with money in their homes who will be able to buy and people who don't."

Back in the east end of Glasgow, Lorraine McEnroe knows she should have tried to get on to the housing ladder years ago. "Hindsight is a fine thing. We could have paid off half a mortgage in the past decade. All we want now is another room and a little bit of breathing space."



A row that shows no sign of subsiding
The argument over the break-up of the country's largest social landlord, Glasgow Housing Association (GHA), shows no sign of subsiding. In 2002, tenants in Glasgow voted to hand over their council homes to GHA in return for a promised £1.5bn in investment over a decade and the split of the body into more than 60 smaller, more accountable, local associations.

GHA officially took over homes just ahead of the 2003 election. But little headway has been made on its original pledge to break itself up, amid claims that to do so would cause a black hole of more than £500m.

Ministers last year reached a compromise under which GHA would be broken up into a smaller number of organisations, including the city's existing community-based housing associations (CBHAs). There were hints made of more money for the process, which is called second-stage transfer, or SST.

Some CBHAs believe they have now found the missing £500m in GHA's business plan. More than half the sum comes from savings critics believe it will make by demolishing more houses than planned, later than planned. Those homes, the argument goes, won't get as much investment as planned and will therefore save GHA money.

That was disputed by Les Campbell, GHA's director of finance. He said: "It is ludicrous to suggest that GHA's business plan includes, or has ever included, £500m to deliver SST."

What the parties say:

Labour Deliver 12,000 new affordable homes each year. Continue investing in social housing, introduce higher design standards and aim for all new housing to be carbon-free by 2016. Every unintentionally homeless person will have the right to a permanent home by 2012 and the party says it will halve child poverty by 2010 and end it in a generation.

SNP
In government, introduce a first-time buyers' grant of £2000 and a nationwide Housing Support Fund to provide shared equity loans to more first-time buyers. Set higher energy efficiency standards and address constraints on affordable housing development. Support extension of household renewable generation to help cut CO2 emissions and energy bills.

Conservative
Form Affordable Homes Trusts (AHTs) worth £100m a year, one-third funded by the state and the rest by developers and investors. Would-be buyers would apply to the AHT for a house, with profits from any rise in value being shared by the trust and the home owners. Seek to change planning culture and release more land for housing.

Lib Dem
Deliver 27,000 new affordable homes for Scotland. Make warm, dry homes a public health priority and end fuel poverty by 2016, improving 40,000 homes a year with a new healthy, green homes fund.

Green
Ensure a decent home for everyone, through expansion of the social rented sector. Local authorities need to set and meet targets for affordable housing in all new developments. Consult on expanding Homestake scheme to help first-time buyers and make it easier for householders to install micropower devices such as solar panels. Improve energy efficiency by 40% by 2020; by 2010, have 65,000 homes built or renovated each year to achieve zero carbon emissions.

SSP
High-quality, low-rent social housing; build 100,000 new homes in four years, financed by cancelling local authority housing debt. Force private developers to allocate one house for social rent for every three new houses built, at rent levels set by the local council or housing association.

Solidarity
Supports the demands by Shelter for 30,000 new local authority homes in three years. The party would end the right to buy and replace it with a right to live rent-free after 25 years' tenancy.