The Queen has been warned that plans to celebrate the 400th anniversary of the union of the crowns could clash with next year's Scottish parliamentary elections.

A senior Nationalist politician said that the Queen was in danger of damaging her reputation in Scotland and alienating Scottish National Party supporters if she became entangled in party politics.

Professor Sir Neil MacCormick, a SNP Euro MP and one of the few Nationalists to accept a Royal honour, said the constitutional position of the monarchy would be damaged if she was seen to be anything but impartial.

Events to mark the anniversary would be a celebration of the unity of Scotland and England at a time when the SNP would be campaigning for independence north of the border.

Sir Neil MacCormick: Wants celebrations moved

The crowns of Scotland and England were united after the death of Elizabeth I in 1603.

James VI of Scotland became James I of England on 24 March of that year.

The 400th anniversary falls just five weeks before the elections to the Scottish Parliament in May 2003.

Sir Neil said he was in "very strongly" in favour of the idea of a constitutional monarch because it puts the issue of loyalty to a head of state outside the run of party political controversy.

However, he said that a celebration "injected into an election campaign would exactly deprive the institution of its point".

Appropriate distance

"By all means celebrate in the summer time when politics are out of the way for a while, but politics and the headship of state should be kept well apart," he said.

"If they were to launch a major celebration during an election campaign they would forfeit their normal and appropriate distance from electoral party politics."

He said ministerial advisers would be at fault if they allowed the Queen to go ahead with the anniversary celebration in March.

Despite being opposed to the union between Scotland and England, the SNP's policy supports a constitutional monarchy.

Its policy states that, come independence, Scots would have the chance to vote in a referendum on whether to retain the Queen as head of state.

If they were to launch a major celebration during an election campaign they would forfeit their normal and appropriate distance from electoral party politics

Sir Neil MacCormick

Labour MP for Glasgow Kelvin, George Galloway, said it was "a bit much" for a Sir Neil - a knight of the realm - to be complaining about the woman who knighted him coming to celebrate a very important milestone.

Conservative MP Michael Ancram said the union had been good for all parts of the United Kingdom and was worth celebrating.

Liberal Democrat MSP Donald Gorrie agreed that the union should be marked but he called for it to be delayed until after the election on 1 May.

Full political union between Scotland and England did not follow until 1707.

This anniversary will also fall in a Scottish Parliamentary election year.