The petition called for withdrawal from Europe's fishing policy

Holyrood's European Committee voted to ask Agriculture minister Ben Bradshaw to the Scottish Parliament.

But committee member and Conservative MSP Phil Gallie said a leaked executive e-mail tried to discourage the Westminster minister from attending.

The petition calls for the UK to be withdrawn from Europe's fishing policy.

A Scottish Executive spokeswoman said: "We are not trying to interfere with the parliament's consideration of the petition."

She said it was appropriate for officials from both the Scottish and UK administrations to advise their ministers on previous practice and protocols about Westminster ministers attending Holyrood.

The executive does not believe withdrawal from the CFP would be in Scotland's best interests, she said.

The e-mail was sent by an executive official to a Scottish fishing organisation following the European Committee's meeting on 28 March.

It has been leaked to Carol MacDonald, a member of Fraserburgh-based fishing campaign group the Cod Crusaders.

'Blurs lines'

She has contacted the SNP and Scottish Conservatives.

The e-mail includes a line saying that the tendency of ministers from the UK government's Department for Environment Food and Rural Affairs (Defra) is not to appear before Scottish Parliament committees.

This is because it "blurs the lines of accountability".

The executive email added: "We and Defra are considering".

Mr Gallie claimed this is interference by the executive in a committee decision and will be contacting the Scottish Parliament's presiding officer George Reid.

'Hijacking'

He said: "This is total interference by the Scottish Executive on the work of the committee and the two are supposed to be separate.

"I will be advising the committee of what is happening and will inform the Presiding Officer George Reid because this breaches all the parliament is supposed to be.

Mrs MacDonald said: "This is not ministerial interference - this is an official hired help.

"This is a devious way of hijacking the Cod Crusaders' chance of telling the truth of the consequences of the current management of the Common Fisheries Policy."

She added: "It is a 250,000-name petition asking that the Scottish Parliament uses its influence on their Westminster peers to get us out of the CFP."