Europe minister Denis MacShane has been threatened with legal action by a French MP.

Arnaud Montebourg, who is backing the No campaign in France's EU constitution referendum, apparently took offence at a suggestion by MacShane that the No vote was backed by "the reactionaries, the neo-conservatives, the neo-communists and les néo-cons".

The Guardian says a "con" is a "popular if vulgar French insult" which translates as "a damn fool; a bloody idiot; a cretin".

"We were shocked and offended by his comments," said Montebourg.

"We have engaged a lawyer and will pursue Mr MacShane in the French courts for the offence of public abuse."

MacShane said he was "truly astonished" and had not intended to cause offence.

"Compared with the insults heaped on my head by anti-Europeans in Britain, my remarks... pale into insignificance," he added.