Around one in three mortgage customers face higher repayment rates and difficulty in borrowing more on their homes in the light of the recent credit crunch.

Lenders have become increasingly cautious following the problems in the credit markets, and as a result many home- owners will be offered less favourable terms if they want to remortgage their homes, market analysts Mintel said yesterday.

Sub-prime mortgage customers - those who typically have a poor credit rating - are becoming less appealing to banks as lenders try to create a more conservative lending climate.

More people than ever are set to fall into the sub-prime category as a result of missed debt repayments, meaning that borrowing will now be put out of reach for many.

Mintel estimates that around 9% of the UK's 16.5 million mortgage holders will now be considered sub-prime by lenders.

It also forecasts that a further 24% could also be considered a high risk because of their personal circumstances, such as being self-employed or not having a regular income, or because they had moved frequently or fallen behind with household bills.

Toby Clark, senior finance analyst, said: "The focus over the last few months has very much been on sub-prime borrowers, but they are only the tip of the iceberg. With lenders becoming increasingly cautious about who they give money to, many more mortgage holders will be offered less than favourable terms when they come to remortgage.

"Those coming off fixed-rate deals taken out before the recent interest rate rises will be particularly hard-hit."

He warned that many people may not be able to absorb these increases and millions of people could start to suffer financially.

The group said in the worst-case scenario people may find they cannot meet their new higher mortgage repayments and fall into arrears that could lead to their home being repossessed.

Research carried out by the group found that one in five people who are planning to get a mortgage in the future already foresee problems because of their income, working status or professional circumstances.

It said 37% of people, or nearly 18 million individuals, could find that they are now classed as being non-standard consumers if they tried to get a mortgage, and this could rise to 20 million by 2012 if lenders continue to tighten their lending criteria.

Mintel predicted demand for non-standard mortgages will continue to grow as people's financial circumstances become ever more complicated due to rising divorce rates and the growing popularity of being self-employed.

But it added that as lenders become increasingly cautious, these mortgages will become harder to get, leaving many people unable to borrow the money they need to buy a home. Other research released yesterday, from web credit specialists uSwitch.com, claimed that one in four people are now struggling with unmanageable debts and 12% admit they have missed repayments during the past six months. Around 23% of people say their current level of borrowing either borders on being unmanageable or is no longer manageable.

The group said 12% of people also admitted they have missed payments on debts or bills during the past six months and 10% have had a payment bounced by their bank because they had insufficient funds in their account.

One in 10 people claim they are now trapped in a vicious cycle of debt where they may need to get further into debt just to meet their existing financial obligations, and 13% may have to turn to credit just to meet their living costs.

At the same time, one in five consumers say they have maxed out at least one of their sources of credit, with 11% going up to their spending limit on a credit card and 10% doing the same on an overdraft.

The research claimed that 38% of people applying for new credit were turned down with 19% of personal loan applications rejected.

The average person now sees half of their take-home pay eaten up by debt repayments, with 35% going on their mortgage and 18% spent on unsecured debts.

Unsurprisingly, 23% of people are now more worried about money than they were a year ago and 18% are more worried about debt.

At the same time 34% say they are feeling financially worse off and more than half of people do not think it is a good time to make a life-changing decision such as buying a home, having a baby or changing jobs.