SNP ministers have extended the deadline for finding a buyer for the last civilian shipyard on the Clyde.

Finance Secretary Derek Mackay told MSPs the marketing of Ferguson Marine in Port Glasgow could take 50 per cent longer than anticipated.

The business, which employs 300 workers, went into administration last month after a £97m contract for two CalMac ferries ran two years late schedule and £100m over budget.

When Mr Mackay took the yard under public control on August 16, he said ministers would nationalise it unless there was a viable commercial offer within four weeks.

However in an update at Holyrood, he marketing it would now last another two to four weeks. He said the priority for ministers was safeguarding jobs and finishing the boats.

He said: “The Scottish Government will at all times remain open to discussions with any parties interested in securing a viable commercial future for the yard. But we will also explore the option of keeping the yard in public ownership, and how this might protect sustainable shipbuilding on the lower Clyde.”

The ferries were ordered by the state-owned firm Caledonian Maritime Assets Ltd (CMAL).

The yard’s former owner, Jim McColl’s Clyde Blowers, blamed CMAL’s design changes for the delays and cost over-runs, while CMAL blamed Ferguson’s “design errors”.

Tory MSP Jamie Greene demanded to know how much nationalisation would cost taxpayers, and demanded a public inquiry into the “fiasco”.

Willie Rennie asked if the CMAL board had threatened to resign en masse if ministers intervened in its dispute with Ferguson’s.

A flustered Mr Mackay passed the buck, saying: “I am not the accountable minister for CMAL.”

Mr Rennie said later: “The Cabinet Secretary tried to dodge this basic question on the resignation of the board but he needs to be transparent with parliament and the public.

“The government needs to come clean and confirm whether or not the CMAL board threatened to resign.”

Labour MSP Colin Smyth said: “Ferguson’s cannot have a secure future if the SNP government remain unwilling to learn from their mistakes. That is why a parliamentary inquiry into this fiasco is needed.

Mr Mackay said the government had always acted in “good faith”.

Green MSP John Finnie said Ferguson’s should stay in public ownership and replace the ageing Calmac fleet.

“The Scottish Government’s acquisition of this yard and its skilled workforce would present an opportunity to deliver joined up procurement and construction processes, with trade union expertise embedded at its heart, to deliver the replacement vessels our island communities so desperately need and the way to guarantee that is to place the yard in public ownership.”