Des McNulty, Labour’s Scottish transport spokesman, has written to the minister asking him to explain statements he gave earlier this year to The Herald that the Scottish Government was committed to the project and that it was on track for delivery before the 2014 Commonwealth Games.

Following the cancellation of the £212m spur from Paisley to Glasgow Airport by the Finance Secretary last Thursday it has emerged that costs were already starting to escalate by early this year.

However, Transport Scotland, the agency responsible for Garl, rejected as “simply false” claims made in the Sunday Herald that it attempted to have responsibility for the project passed to Network Rail, the not-for-profit company that runs the railways, last spring.

Following the emergence of doubts about whether it would be completed on schedule, Mr Stevenson told The Herald in July that the project was not in trouble. “Ministers are committed to the delivery of the Glasgow Airport Rail Link and any reports to the contrary are inaccurate,” he said at the time.

In a letter sent to the Transport Minister, Mr McNulty called for the “inconsistencies” in the government’s position to be explained.

“If Transport Scotland had serious concerns about the project, these should have been highlighted earlier by ministers and/or officials. There were plenty of opportunities – including most recently the session of the Transport Committee last week where Mr Swinney was questioned about Garl,” he wrote.

The Clydebank and Milngavie MSP said he was also trying to discover whether any comparison had been done to establish whether Garl represented poor value for money compared to other major infrastructure projects.

“If Garl has been cancelled for financial reasons then it’s important that we know whether a value for money comparison had been made with other big projects such as the Borders Railway Project and Aberdeen Western Peripheral Route.

“It simply makes no sense in transport terms to cancel rail links to the country’s two biggest airports,” he said.

Uncertainty over the eventual cost of Edinburgh’s tram system, which is due to breach its £545m budget, has been cited by the SNP’s Glasgow MSP, Sandra White, as contributing to the decision to cancel Garl. Though the government, which opposed building the trams, has insisted it will contribute “not a penny more”, there is speculation that ministers will eventually have to step in with financial help.

A spokeswoman for Transport Scotland said that escalating costs had only been a contributing factor in cancelling the rail link. “(The) Cabinet Secretary made it clear last week the reasons for cancellation of Garl were on the grounds of affordability and while the change in scope and cost reasons referred to last week were a contributing factor, it was the overall financial situation that led ministers to take the decision,” she said.