French prosecutors have announced that a formal police investigation has been opened into a “Nazi-themed” stag party attended by a Conservative MP.

Aidan Burley, MP for Cannock Chase, lost his job as Private Secretary to Transport Secretary Justine Greening after being filmed at the event in the Val Thorens ski resort last year.

At the party, one guest donned the uniform of the SS and others allegedly toasted the Third Reich and architects of the Final Solution, Heinrich Himmler and Adolf Eichmann.

Local prosecutor Patrick Quincy said on Wednesday that following a preliminary investigation, the French authorities were now moving forward with a full official probe into what happened.

He said that police would look at charges including wearing the uniform of an organisation that perpetrated crimes against humanity and making racist slurs.

Last year fashion designer John Galliano was convicted of public insult and antisemitism under French anti-racism laws.

Ian Austin, a Labour MP and the adopted son of a Jewish man who fled Nazi Germany, said that the formal investigation showed that it was time for the Conservative Party to withdraw the whip from Mr Burley.

Prime Minister David Cameron asked for a fuller investigation of the matter in Britain, but so far the results have not been made public.

A Conservative Party spokesman declined to comment on whether the whip would be withdrawn, but he said that a summary of the findings of the investigation would be published by the end of February. He said the findings would be made available to all interested parties.