MINISTERS have been told to come clean about spending on Prestwick Airport after a public spending watchdog revealed that the Scottish Government expected to hand over £40 million of taxpayer loans by 2021.

Scottish Labour has demanded a ministerial statement following revelations which emerged in an Audit Scotland report on Tuesday.

A revised business plan drawn up by the Scottish Government in May 2014 calculated that the airport was likely to require a total of £39.6m of public investment by 2021/22, some £15m more than had already been announced.

The figures were not disclosed to parliament nor revealed by then Deputy First Minister Nicola Sturgeon during two subsequent appearances before Holyrood's infrastructure committee.

Scottish Labour Infrastructure Spokeswoman Mary Fee said: "The SNP did not tell the Scottish Parliament and the Scottish people that the investment needed was nearly £40 million when they had at least two separate opportunities to do so. That simply is not good enough.

"The SNP Government should deliver a statement to Parliament as soon as possible to explain why this information was withheld, and give workers and tax payers alike the proper story."

Transport Scotland said the figure was only an estimate and "subject to revision".