The SNP’s ferries fiasco has deepened after it emerged one of the delayed and over-budget vessels already needs replacement parts.

Worn or malfunctioning components on the Glen Sannox, which was originally due to be finished six years ago, but is still not ready, are being replaced with parts stripped out from its sister ship, the Glen Rosa, which is also yet to set sail.

The two ferries were due to enter service in 2018 and 2019, respectively, at a cost to taxpayers of £97 million. However, they remain unfinished and the total costs have spiralled to close to £400 million… The parts moved from one ferry to the other are believed to include cables and pipes.

The Glen Sannox was undergoing sea trials and had been due to be handed over to operator CalMac this month. However, this was delayed again when problems were detected in the tests, with a new handover date yet to be announced. Currently the Glen Rosa is due to enter service in September next year.

Ferguson Marine won the contract to build the vessels in 2015, the year after the yard was saved by Jim McColl, then a prominent pro-independence businessman.

Ferguson Marine confirmed that parts from the Glen Rosa had been removed and installed in the Glen Sannox, but denied that this would impact the completion date. Sue Webber, the Scottish Tory shadow transport secretary, said the assurance was “hard to believe”…  Ripping out parts of Glen Rosa to replace those on the Glen Sannox is robbing Peter to pay Paul.

“Scotland’s betrayed islanders are sick of the endless delays, incompetence, and excuses which SNP ministers have presided over, while taxpayers are carrying the can for the ever-spiralling costs.”

The ships are due to serve island communities on Scotland’s west coast, which have been plagued by regular breakdowns of the ageing existing fleet.

A spokesman for Ferguson Marine said: “Some parts have been taken from MV Glen Rosa for use on MV Glen Sannox.

“Given we are due to hand over Glen Sannox soon, this is quicker than ordering replacement parts or fixing them. It will not delay the delivery of Glen Rosa.”