Workers at the BiFab marine engineering yards in Fife and Arnish on Lewis will be issued with redundancy notices on Tuesday, according to union officials.

Unite said the move will give 45 days notice that the yards are to close.

The union said some 260 jobs are to go by May and the yards could be completely closed by the end of June.

Unite's regional officer Bob McGregor says: "So much has been done to save these yards until now.

"The workers there have fought for their future and it is difficult to believe that it can now be snatched away from them.

"The closures of these yards will turn these areas into an industrial graveyard.

"The prospect fills us with dismay."

Last November the BiFab yards were threatened with closure but the Scottish Government said an agreement had been reached to prevent the engineering business going into administration.

The move followed talks between ministers and Dutch-based Seaway Heavy Lifting, which was in dispute with BiFab.

The deal meant work continue on its current contract for the Beatrice Offshore Windfarm.

But on Monday night the union said BiFab is now running out of work as the contract is coming to a close.

Mr McGregor added: "We can't say this is a total shock because work at the yard has been running down for weeks now.

"However all the interested parties, the company, the contractors, the unions and the Scottish Government, given what has been done so far, must surely look to have an eleventh hour intervention which can do something to save these jobs."

Earlier on Monday the BiFab management told unions the first redundancies would start in May and the closure would be completed by the end of June.

These timescales can only be reversed if new contracts can be established for the yards.

Economy Secretary Keith Brown said: "This will be hugely concerning for the workers affected and their families.

"Scottish ministers have offered support to BiFab to allow work to continue on the contracts for the Beatrice offshore wind farm development through a loan facility and have been fully focused and working intensively to secure a long-term future for the company.

"Ministers recognise that more work remains to be done to secure the long-term future of the company and are fully committed to offering support where possible to attract long-term investment in this vital sector of the Scottish supply chain and economy."

Claire Baker, MSP for Mid Scotland and Fife, hosted a cross-party meeting on Wednesday at the Scottish Parliament to discuss the yards.

She said in a tweet: "After a Parliamentary show of support last week for BiFab workers this must be challenged - these jobs are vital for Fife economy and our future industry base."

No-one from BiFab was available for comment.