Prime Minister David Cameron proved the British political right is the world's stupidest by refusing last week's European summit deal on fiscal reform under pressure from narrow financial lobby interests, the head of France's financial sector regulator said Monday.

For a long time it was said that the French right was the world's stupidest, Jean-Pierre Jouyet, head of France's AMF regulatory agency, said in an interview on France Inter state radio.

I think the English right has shown it is capable of being the world's stupidest, in serving purely financial interests and not the national interest. That's regrettable because we need our British friends in Europe.

Cameron's refusal to sign up to the deal agreed at a summit in Brussels last Friday was a rare example in the history of the European Union where financial sector interests prevailed over broader British interests, said Jouyet, once a chief aide to former European Commission chief Jacques Delors and a European affairs minister as well as French Treasury director.

It was all the more striking, said Jouyet, given that more than 2 million British workers recently protested against austerity measures in a country with a public deficit worth eight percent of GDP and debt worth 80 percent of GDP but pay rises averaging 49 percent this year on average for bankers.

(Former Prime Ministers Tony) Blair and (Gordon) Brown would not have made this error in negotiation, said Jouyet, who has advised Socialist presidential candidate Francois Hollande.

Cameron was left out in the cold last Friday when France and Germany refused to give him the safeguards he wanted for the powerful City of London financial services industry during talks on fiscal policy reforms in response to the debt crisis in Europe.

(Reporting By Brian Love; Editing by Rosalind Russell)