First Minister Alex Salmond met Donald Trump's representatives the day before ministers decided to have the final say on his golf resort plans.
The £1bn proposals for Aberdeenshire's Menie Estate were rejected by the local authority but were "called in" by ministers last Tuesday.
Mr Salmond is forbidden to take part in the planning process.
He insisted that because the plans fell into his Gordon constituency, he was duty bound to meet people on all sides.
Despite the assurance, opposition parties have expressed concerns that the meeting, last Monday at the five-star Marcliffe hotel in Aberdeen, took place.
BBC Scotland has also learned that the Scottish Government's chief planner, Jim McKinnon, held his own talks with Mr Trump's team.
The government said it was to explain the role of Scottish ministers in planning applications and appeals.
Ministers stepped in after the controversial application was rejected when it went before Aberdeenshire Council's infrastructure committee, on the casting vote of its chairman.
The issue, said the government, required consideration at a national level.
Labour MSP Johann Lamont told BBC Scotland's Politics Show that, during her time as a planning minister, she was advised to be "very cautious" who she met on planning matters.
She added: "This feels very uncomfortable and says something very odd about Alex Salmond's trumpeted new relationship with local government.
"He believes in a partnership with local government, they take their responsibilities seriously. Apparently he then just moves in when he doesn't like the answer he's getting."
Tory parliamentary business spokesman David McLetchie said people would "smell a rat", adding: "There are already lots of concerns about the decision to call in the application.
"This will confirm many people's fears that this application is now a shoe-in and it's going to be rubber-stamped by the Scottish ministers, irrespective of what was decided locally."
Lib Dem Aberdeenshire MSP Mike Rumbles said the meeting had demonstrated a lack of openness and transparency.
"I would be astounded if Alex Salmond was holding a constituency advice surgery at the Marcliffe hotel," he said.
"He is responsible for the ministerial code of conduct, which says that you shouldn't even give the appearance of a conflict of interest.
"There are a huge number of questions here and it does smell, I'm afraid."
George Sorial, Mr Trump's main representative in Scotland, would neither confirm nor deny the Marcliffe talks, because "things are so sensitive right now".
Mr Salmond said: "As the constituency MSP, not only am I absolutely entitled but I have a bounden duty under the parliamentary code to meet people on all issues of importance to my constituency.
"I have met people on both sides of the debate. Last Monday, I met members of the Trump organisation in Aberdeen.
"As first minister I have been advised to make no public statement either for or against the proposed development, and I have abided by that to the letter."
Mr Salmond has met with critics of the development, including local farmer Michael Forbes and the campaign group Sustainable Aberdeenshire.
However, the group's David Milne said: "We only succeeded in getting contact with him at his constituency office a couple of months ago after some considerable effort."
Finance Secretary John Swinney will have the final say on the Trump International Links scheme, which would include two championship golf courses and 1,500 homes.