Mr Swinney said the Waverley line finances must be "robust"

Work has already started on the Borders rail link, which will run from New Craighall in Edinburgh to Tweedbank.

Mr Swinney confirmed the 35-mile route was one of the major transport projects which the administration was studying.

He was responding to a question raised by Borders MSP Jeremy Purvis about the financial future of the scheme.

"The Borders rail link is one of the projects we are looking at very closely to ensure that all of the financial assumptions are robust," said Mr Swinney in the parliament.

We would be failing in our duty if we did not try to satisfy ourselves about all of those projects, and that includes the range of projects being developed by Transport Scotland Stewart Stevenson Transport minister

"We have got to do that.

"If we were not doing that, we would be failing in our duty."

Mr Purvis had raised concerns that the costs of an Edinburgh Airport link might leave no money for the Borders scheme.

He asked Mr Swinney to confirm that the Waverley line was not covered by a recently announced review of major transport schemes.

Mr Swinney said the government had an obligation to look at every project - including the Edinburgh to Tweedbank line.

'Programme list'

Transport Minister Stewart Stevenson said the government would return to parliament with information on the review of these projects.

"We are a new government, we have inherited a programme list from the previous administration," he said.

"We would be failing in our duty if we did not try to satisfy ourselves about all of those projects, and that includes the range of projects being developed by Transport Scotland."