Image copyright Reuters

A US Congressional committee is investigating President Donald Trump in connection with a potential conflict of interest over military spending at a Scottish airport near his golf resort.

The House Oversight and Reform Committee says expenditure at Prestwick airport has "increased substantially" since Mr Trump came into office.

The debt-ridden airport has been fighting off closure.

It is said to be integral to the Trump business, which is also loss-making.

The committee's accusations are detailed in a letter to the Pentagon - which is dated to June but was only revealed on the Politico website on Friday.

The letter requests access to all communications between the US Department of Defense and Trump Turnberry, as well as any related financial records.

According to various reports in the US media, the department has not yet complied with the demands.

It has also not commented directly, and neither has the Trump Organisation.

What does the letter say?

The letter - signed by the Democratic committee chairman Elijah Cummings - was addressed to then-acting Secretary of Defence Patrick Shanahan.

Media playback is unsupported on your device Media caption Donald Trump on the Turnberry golf course in 2014

Citing Defence Logistics Agency (DLA) records, it said the US military had made 629 fuel purchase orders at the airport, totalling $11m (£9m), since October 2017.

It also alleges that certain military personnel have been offered "cut-price rooms" and free rounds of golf at the Trump Turnberry resort.

It continued: "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."

Who owns the airport?

Prestwick airport, south of Glasgow, is approximately 20 miles (30km) north of Trump Turnberry.

The Scottish government bought it for £1 in 2013, when it was facing closure.

In June, it was put up for sale. No buyer has been announced.

Image copyright Getty Images Image caption Air Force One seen at Prestwick Airport during the president's 2018 visit

Amid rising debts, the airport has reportedly slashed its charges to try to retain business.

The Scottish government faced a backlash in 2017 after the Turnberry resort received a tax rebate. Later that year, the rules changed and it no longer qualified.

Responding to the latest allegations, the Scottish government said Prestwick Airport operates on a commercial basis and at arm's length from ministers.