Lord Mandelson has been accused of leaking inaccurate details of John Swinney's whisky trade talks with Trump to the media.
The UK's former ambassador to the US is reportedly the prime suspect for putting the deal at risk for briefing an account of his private talks to reporters.
Days after the first minister's meeting with the president in September to push for a tariff-free whisky trade deal, it was reported Swinney had voiced his support for Trump's renovation of the East Wing in the White House.
He reportedly told him “if you’re going to do it, you might as well go big."
Mandelson, who is under police investigation over claims he passed state secrets to the disgraced Jeffrey Epstein, was one of four people in the room during the talks.
While the first minister's team cannot prove Mandelson was the source of the leak, the team believe it was unlikely to come from president Trump, Swinney or Marco Rubio, the US secretary of state.
Senior Scottish government sources were appalled at the leak, fearing it could have put the trade deal at risk.
“At the highest level, everyone understands that there has to be a confidential space in which world leaders can speak frankly and directly,” a source said. “That’s how deals get done.
“The talks with Trump were incredibly sensitive. If the ambassador is leaking details of that discussion — even relatively minor details — it fundamentally undermines our ability to get a deal for Scotland.
“When Scottish jobs and Scotland’s economy are on the line, discovering the UK’s ambassador was apparently undermining Scotland’s chances of getting a deal is jaw dropping.”