US military flights to and from Prestwick Airport should be suspended while a Congressional committee investigates its role in a growing row involving Donald Trump, it has been demanded.

Scottish Greens co-leader Patrick Harvie said Scotland risked having its international name “dragged into a corruption allegation against a far-right US President”.

The House Oversight and Reform Committee said US military spending at Prestwick, the closest airport to the Trump Turnberry golf course, has “increased substantially” since Mr Trump’s election.

In a letter sent to the Pentagon in June, but only publicly revealed by the US news outlet Politico on Friday, it raised "serious conflict of interest concerns".

Mr Harvie said: “Controversy around the use of Prestwick by the American military has been long-standing, including extraordinary rendition flights and active military missions. Scottish Greens have repeatedly raised this in Parliament.

“The fact its use is now being investigated by US Congress risks Scotland’s reputation being dragged into a corruption allegation.

"We should not stand by as Scotland’s good name is tarnished by association with the toxic Trump brand.

“That is why I have asked the minister to at least suspend the relationship, until the investigation is concluded.

“What’s more, the Scottish Government has put this publicly-owned airport up for sale and the minister said the sale was progressing.

"Who on earth would buy an airport with this reputation, and what would they use it for?

“If Prestwick is to be used for the public good, the site should be transitioned into a low-carbon alternative, not sold to the highest bidder.”

The letter revealed last week was signed by Elijah Cummings, chairman of the House Oversight and Reform Committee. 

It said Prestwick had reportedly provided “cut-price rooms for select passengers and crew” and offered “free rounds of golf at Turnberry to visiting US military and civilian air crews”.

It added: “Given the President’s continued financial stake in his Scotland golf courses, these reports raise questions about the President’s potential receipt of US or foreign government emoluments in violation of the US constitution and raise other serious conflict of interest concerns.”

The committee has requested access to all communications between the US Department of Defense and Trump Turnberry, as well as documents relating to expenditures.

It said the Defense Logistics Agency – the Department of Defense's combat logistics support agency – had made 629 fuel purchase orders at the airport, totalling $11m (£9m) since October 2017.

At Holyrood, Transport Secretary Michael Matheson was asked to confirm how much Prestwick has received from the US military for its operations.

He said the airport operates at arms-length, but insisted it has no “commercial relationship” with Trump Turnberry.

The Scottish Government bought Prestwick for £1 in 2013 to prevent its closure. 

The debt-laden airport was put up for sale earlier this summer.