Scottish Conservative leader Russell Findlay says the SNP's ongoing ferries fiasco is one of their most appalling failures during their two decades in power.
Findlay made the call ahead of a campaign trip to Ayrshire, where he was due to visit both Ardrossan and Troon harbours.
He says the situation is a totem of SNP incompetence of which John Swinney should be utterly ashamed.
Around a third of CalMac's fleet is currently out of action, including the Glen Sannox which was seven years late before it finally entered service last year.
Its sister ship, the Glen Rosa, is not due to be completed until after the election at the earliest and the two ferries being built by SNP-run Ferguson Marine have now cost Scottish taxpayers close to £500 million.
Findlay says it is shocking no one has been held to account over the corrupted CalMac procurement process.
He added that Swinney’s claims today that he’s on the side of islanders sounds like he’s “gaslighting islanders and taxpayers.”
Scottish Conservative leader Russell Findlay said: “The ferry fiasco is a totem of SNP incompetence of which John Swinney should be utterly ashamed.
“They've failed island communities by squandering around half a billion pounds on two dodgy vessels that will never be right.
“For John Swinney to now have the audacity to claim that he's on the side of islanders sounds like he's gaslighting islanders and taxpayers. He's beyond shame.
“For this reason alone, Scots should use their peach ballot paper to vote Scottish Conservative on May 7th to help stop an SNP majority.”