Andreasen was suspended in May and again in August after saying there were failures in the European Union's accounting system and warning its £69bn annual budget was open to fraud and abuse.

The Tory MEPs are today expected to accuse Kinnock of dismissing Andreasen despite the existence of an internal report which appears to endorse many of her allegations.

The calls for resignation are being led by Chris Heaton-Harris, MEP for the East Midlands who is expected to challenge Kinnock on the letter, alleged to have been written days before Andreasen's first suspension in May.

In December of last year, Andreasen was formally asked to stand as a Tory candidate in Wales, standing against Kinnock's wife, Glenys in next year's European elections.