Christine McCartney

A new bridge is to be built across the Firth of Forth at a cost of £4.2bn, Finance Secretary John Swinney announced yesterday.

The crossing is expected to be ready by 2016 and will be a replacement for the existing road bridge, which experts have warned may have to be closed to all vehicles by 2019 due to erosion of its suspension cables.

Mr Swinney told the Scottish Parliament he had rejected the option of building a tunnel and had instead decided upon a so-called "cable-stayed bridge" running from the northern shore of the Forth to a point west of South Queensferry.

It will be the largest construction project in Scotland for a generation and Mr Swinney predicted it would become "an iconic structure".

As well as normal road traffic, the new bridge will also be used by pedestrians, cyclists and public transport such as buses, light rail or trams.

Mr Swinney said the government intended to use the planned Scottish Futures Trust to pay for the bridge as an alternative to the Public Private Partnership. He insisted it would not be tolled.

With the long-term future of the existing bridge in doubt, Mr Swinney said "doing nothing is not an option".

He said: "The Forth Rail Bridge created an image of global significance when it was constructed in the 19th century. Our vision of a new crossing of equal stature and significance is the government's promise today."

Opposition parties were broadly supportive of the decision, but demanded more details on how it will be paid for. Environmental campaigners also dismissed the plans as "premature" and warned the new crossing will generate more traffic and hamper government attempts to reduce greenhouse gas emissions.

In his statement to parliament, Mr Swinney said the government had considered four options - two types of bridge and two tunnel designs. He said that at five-and-a-half years, the cable-stayed bridge would be the quickest to build, and was also the cheapest option, costing between £3.25bn and £4.22bn.

Mr Swinney said the tunnel option was more expensive, would take longer to complete and would not be suitable for light trains or trams. He also pointed out that lorries carrying flammable liquids such as oil and whisky would be banned from using it.

"Having assessed all these factors, the government has come to the view that the Forth replacement crossing should be a cable-stayed bridge," he said.

Approach roads will connect the new crossing to the M9, while work will be carried out to soften the environmental impact of the construction process.

The next three years will be spent passing the necessary legislation, choosing the contractors and finalising the contracts before building work starts in 2011.

Mr Swinney added: "We are supporting commuters, supporting business and protecting the environment. This crossing will ensure that we continue to provide an effective transport network and achieve that goal."

Labour, the Conservatives and the Liberal Democrats all called on the government to produce more details on the procurement process and Mr Swinney said an announcement was "imminent".

Business leaders were unanimous in their backing for the plans. Liz Cameron, chief executive of Scottish Chambers of Commerce, said: "The selection of the cable-stayed bridge option is a sensible one, which should ensure that we have a fit-for-purpose bridge, deliverable within the shortest possible construction period."

But Dr Dan Barlow, the acting director of environmental campaigners WWF Scotland, said: "With work still under way to review the options for repairing the existing bridge, the government's decision to proceed with developing proposals for a new Forth road bridge is premature.

"Rather than committing £3-4bn to a new crossing, the government should instead be implementing measures to tackle congestion and improve public transport."