Thousands of Scottish shipyard jobs are in the balance after it emerged that work to build two aircraft carriers may be delayed by the financial downturn.

The contract for the 65,000-tonne vessels HMS Queen Elizabeth and HMS Prince of Wales was signed in July. Work was due to commence on the warships - the biggest to be built in the UK - at the Govan yard in Glasgow next spring.

However, the Ministry of Defence is now reviewing all of its main investments in an attempt to make savings as the economic climate worsens.

The move has prompted concerns among shipyard workers that there could be “slippage” in the contract to construct the aircraft carriers.

A spokeswoman for the MoD said: “The MoD is looking at all its major equipment programmes over the next 10 years, with a view to bearing down on costs and making sure the frontline troops are being properly supported.

“We hope this work will conclude soon, but at the moment no decisions have been made.”

There was jubilation at Govan when the contract for constructing the so-called super-carriers was finalised in July after months of delay. Workers said it would create a level of job security that had not been enjoyed at the yard for a generation.

The project was to be split between yards at Govan, Rosyth, Portsmouth and Barrow-in-Furness. The contract, estimated to be worth £4.25billion, included £1.3billion for giant sections of both ships to be built in Glasgow and Portsmouth, £300million for the construction of giant sections at Barrow, and £675million for the bow section and final assembly of both ships at Rosyth. Constructing the 65,000-tonne carriers was expected to create or secure 3,000 jobs at Govan, and 1,600 jobs at Rosyth, as well as supporting another 1,600 jobs at the English yards.

Fears are now growing that the huge jobs boost will be jeopardised. “We are hearing rumblings that the MoD are going to be postponing the work,” a senior source at the Govan yard said.

Union leaders urged the Government to come clean about their intentions. Jamie Webster, convenor for GMB at Govan, said: “I wouldn't be surprised if the contract was extended, but if that is the case the MoD must come out and declare it.”

Opposition MPs greeted the MoD review with dismay.

Angus Robertson, the SNP MP and leader of the party at Westminster, said that any delay would be highly damaging.

“At a time of great economic uncertainty and global insecurity, it would be a mistake for the MoD to slow down defence projects,” he said. “The workforce on the Clyde are highly skilled and ready to get on with the super-carrier project. The MoD must do a better job persuading the Treasury to go ahead with important procurement work.”

Willie Rennie, the Scottish Liberal Democrat MP who is also defence spokesman for the party at Westminster, said: “If this is just an efficiency drive it would be welcomed, but if they're talking about slashing the contract there would be fury at the yards.”

Ian Davidson, the Labour MP whose Glasgow South West constituency includes the Govan yard, cautioned against panic. “Even if there is a delay with the aircraft carriers, it's not necessarily a bad thing so long as the yards are kept occupied,” he said.

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