"The handling of this case has raised a number of matters of principle."

As shocking as it may seem, turns out that the sudden approval of The Donald's Scottish golf course may not have been entirely on the up and up.

Eddie Barnes reports for Scotland on Sunday:

In a highly unusual move, the national director of the Royal Town Planning Institute (RTPI) has written to Finance Secretary John Swinney, reminding ministers of the need to be "politically impartial" and "transparent" when handling planning applications. Dr Veronica Burbridge warns Swinney that her members have been in contact to "express concerns" about the way the case has been handled.

The move follows a week of turmoil after ministers decided they, not the local council, would decide whether plans by American tycoon Donald Trump to build a huge golfing complex in Aberdeenshire should go ahead.

It emerged that a day before the decision, First Minister Alex Salmond, who is also the local MSP for the area, met two of Trump's representatives to discuss the case.

It then emerged that the pair had also met the Scottish Government's chief planner on the day the decision was made.

The matter led to a bitter political row which continues to rage, with opposition parties accusing Salmond of "sleaze", while the SNP accused them of risking an investment of up to £1bn.

In the RPTI letter, Burbridge states: "The handling of this case has raised a number of matters of principle. Members of the institute have expressed concerns that the manner in which this case is handled should not appear to damage the integrity of the planning system."

It adds: "They stress the need to ensure that procedures are transparent, respected and clearly understood by all those involved. Members of the institute are concerned that the approach to scrutiny of this case should be politically impartial and according to planning law and planning policy."

Opposition parties seized on the letter last night, claiming it supported their own concerns.

Scottish Lib Dem leader Nicol Stephen said: "This is an exceptional move which underlines the seriousness of the institute's concerns. This matter has grave implications for the conduct of Government.

"Ministers are ultimately responsible for the actions of Government and there is a fundamental lack of transparency and openness in the SNP Government's approach to this issue."

Swinney is expected to make a statement to Parliament this week answering questions about the Government's handling.

No one was available for comment from the Scottish Government.