MSPs will push for ministers to resign if the timetable for the completion of two delayed and over-budget ferries slips again.

Finance Secretary Kate Forbes told MSPs last month that the Glen Sannox and as yet unnamed hull 802 will be delayed until at least next year – five years later than planned.

The cost of the final project are estimated to be as high as £240 million, almost two-and-a-half times higher than the original £97m budget.

Both are under construction at the Government-owned Ferguson Marine shipyard in Port Glasgow, which was saved from administration in 2018 when a number of problems were discovered.

The yard has come under scrutiny repeatedly at Holyrood,with an Audit Scotland report revealing that ministers went ahead with the contract despite a full refund guarantee not being on offer and concerns raised by ferry procurement body, Caledonian Maritime Assets Limited (Cmal).

In a debate today, the Scottish LibDems will seek to force the resignation of the responsible minister if the timetable is missed again.

“Ministers have ducked and dived, desperate to shirk responsibility for too long,” said the party’s economy spokesman, Willie Rennie.

“These delays have left islanders and communities without reliable services, critical to island life.

“In a just world, past ministers who left island communities without lifeline services and oversaw hundreds of millions in cost over-runs would hand in their resignation.

“There are no guarantees that these colossal failures will not simply be allowed to repeat themselves.

“That’s why Scottish Liberal Democrats believe that if these boats are not finished on time, the responsible minister should resign. That is the principle that we are asking parliament to back.”

The wording of the motion calls on the Scottish Parliament to agree that “if vessels 801 and 802 are not completed within the revised timescale and cost provided to Parliament on 23 March 2022, the latest in a string of revisions, then the ministers responsible deserve to finally be held to account in the form of resignations and calls on the Scottish Government to give this assurance.”

Given the co-operation agreement between the SNP and the Scottish Greens in Holyrood, the motion is highly unlikely to pass.