A Paris judge has charged the incoming chief executive of Total, the French oil and gas group, with corruption during the scandal-plagued United Nations oil-for-food programme in Iraq.

Christophe de Margerie, Total's head of exploration and production, was imprisoned for 48 hours and questioned by judicial police and a judge, before being charged with aiding and abetting corruption of foreign officials and misuse of company property.

He was released from custody on Thursday. The surprise move cast a shadow over plans for Mr Margerie to replace Thierry Desmarest as chief executive when the latter steps up to non-executive chairman after the group's annual results in February.

But Total insisted the succession would proceed as planned. "Presumption of innocence is absolute and so life goes on," said Catherine Enck, spokeswoman at Total. The French judicial system can often put people under investigation for years, sometimes without their ever going to trial.

"The group would like to reassure Mr de Margerie of its solidarity. Total confirms that at no time did the group circumvent the United Nations embargo against Iraq and strictly adhered to the rules of the oil-for-food programme," the company said.

The move is a setback for the image of France's biggest company, which has a market capitalisation just short of €130 billion ($163 billion) and employs 95,000. Yet analysts shrugged off the news, and Total shares rose 50 cents to €53.70.

Mr de Margerie (55) was head of Total's activities in the Middle East between 1995 and 1999. He is well respected in the industry as an outspoken expert on the Gulf's oil sector. His lawyer, Olivier Rosenfeld, said the charges were "without foundation".

The charges add to discomfort in Paris political and business circles about the damage being done to France's prestige by the inquiry.