EDINBURGH and Fife could be left without a Forth crossing unless work on a new road bridge is under way by next year, the Forth Estuary Transport Authority has warned.
Lawrence Marshall, the convener of FETA, said it could take up to 11 years for a new bridge to be completed.
He warned that with the current structure facing closure in 2019 if attempts to repair corroded cables fail, commuters could be left with no convenient way to cross the Forth if work on a replacement does not begin soon.
He also confirmed that a new structure would not be ready in time for the expected 2014 ban on lorries on the current bridge if repair efforts failed.
However, Mr Marshall also cautioned that a full study must be completed before a decision is taken on another crossing .
And he said that, although a new bridge could take ten to 11 years to complete - including a likely public inquiry - a year could be saved if the Executive pushed it through.
Mr Marshall added: "It's going to be tight. Having to close the bridge to lorries would be a concern, but what I'm worried about is complete closure."
He said an independent assessment, which is due to be completed for the Executive within weeks, would simply look at the cable investigations already carried out by FETA. It would not be clear until next year whether repair options should be pursued rather than pressing ahead with a replacement bridge, he said. These focus on blowing dry air into the main cables in an attempt to arrest the corrosion, which could cost 12 million, or installing new main cables, which could cost 100 million.
His comments followed the statement by Alistair Darling, the Scottish Secretary and Transport Secretary, that a new bridge would be required, even though the Executive has said it is too early to make such a decision.
Mr Darling said: "It's now clear that the existing Forth [road] bridge is not going to last as long as people thought ... it would be absolutely ridiculous were Fife left without a bridge".
However, Mr Marshall said it was ironic that the minister had called for a new bridge - costing at least 500 million - without detailed plans. By contrast, he said Mr Darling had delayed or scrapped several major English transport projects, such as tram schemes, after ordering them to be re-assessed.
Mr Marshall said Mr Darling was not taking a properly considered approach: "Due process has been short-circuited."
Tavish Scott, the Lib Dem transport minister at Holyrood, is expected to join the attack today on Mr Darling's intervention in a devolved issue.
Jack McConnell, the First Minister, has said a decision on what action to take on the bridge corrosion will be taken before the Executive rules on FETA's application for approval in principle to vary tolls.
An Executive spokesman said this was expected within weeks, but stressed that ministers may decide to await further investigation work rather than decide immediately whether a new bridge is required.