"You will certainly be keen to take part in the coming national debate. It is only fair you should be able to do so," Chirac told cabinet ministers.

"But you must do so with respect for one clear principle: taking part in the electoral debate must in no way undermine your work in government."

Chirac appeared to be taking aim at Sarkozy, who is expected to be anointed as the UMP's candidate at a party congress on January 14, but has yet to say when he plans to leave the government to focus on the race.

Critics see a conflict of interest in Sarkozy's job as interior minister -- and therefore technically in charge of organising the April 22 elections -- and question his ability to keep his eye on the job while on the campaign trial.

Brice Hortefeux, a close Sarkozy ally, said Wednesday that to juggle both roles was "all a question of ability -- and Nicolas Sarkozy has more than enough of that."

He dismissed grumblings about a conflict of interest, saying today was "not the 19th century, when interior ministers... organised the candidacies and chose the winners" of French elections.

But others among Sarkozy's friends are advising him to stand down right away, to clear the air.

Besides, ruling party members concede that the choice may not be entirely his -- Chirac has the power to force Sarkozy out of government if he believes he can no longer combine the roles of minister and candidate.

The animosity between Chirac, 74, and Sarkozy, 51 -- a former protege who "betrayed" him by backing a rival presidential candidate in 1995, going on to wrest control of the UMP, founded by Chirac -- is an open secret in French politics.

In his New Year's address to the nation, Chirac pointedly refused to rule out running for a third term and -- though a bid is seen as highly unlikely -- looks set to allow the suspense to linger up to the last moment.

Chirac's refusal to step aside has undoubtedly taken some of the wind out of Sarkozy's sails -- although polls still show him neck-and-neck with his Socialist rival Segolene Royal, who is riding a wave of enthusiastic support for her bid to become France's first woman president.

The president also took aim Wednesday at Sarkozy's campaign call for a "clean break" with France's Gaullist tradition, in favour of an American-inspired approach to economic and social reform.

He warned ministers against the "temptation of the clean slate" and urged them to show "respect for work done".

Both Sarkozy and Royal, 53, have promised to sweep aside many of the features left by Chirac's almost 12 years in power, threatening the incumbent president's hope of leaving a strong legacy.

Twenty-six percent of respondents said they would abstain in the election or spoil their vote.

The Socialist candidate was also seen as the frontrunner for the first round, with 34 percent of the votes, up three points, ahead of Sarkozy with 32 percent, up two points.

Far-right politician Jean-Marie Le Pen, who made it to the runoff vote in the 2002 presidential election, was credited with 15 percent of the votes, down one point.

France votes on April 22 and May 6 to find a successor to incumbent Jacques Chirac, who has not ruled himself out of running for an unlikely third term.

It also underlined Royal's attempts to bolster her credibility domestically and internationally after months of sniping from detractors that the 53-year-old candidate of the opposition Socialist Party was a political lightweight.

"If France is having a hard time, it's not for lack of advantages -- it's because its leaders have wasted them," she said in a speech conveying New Year's wishes to the public.

She outlined a platform of promises whereby, under her, the French would benefit from "an exercise of power that is simple, direct and genuine".

Royal proposed improving housing security, especially for families and the homeless. That responded to a government bill announced Wednesday that went in the same direction following pressure from a left-wing group that brought the issue to the fore over the past two weeks.

She also argued for a reform of France's generous welfare system that would reward active job-seekers and offer better child-care options for working parents, and pledged to ensure France had influence over EU labour laws.

Later Thursday, Royal was to give details of a trip to China that would see her and a 15-strong delegation speaking to top officials, including possibly President Hu Jintao. The visit would run from Saturday to Tuesday, with Royal leaving late Friday.

China "is an enormous emerging power" whose increasing clout in the globalised marketplace "makes the French nervous," Royal's campaign manager, Jean-Louis Biano, told AFP.

Polls already show Royal leading the race to succeed 74-year-old Chirac in the presidential elections, due in two rounds on April 22 and May 6.

The latest survey, carried out by the CSA institute and published Thursday, predicted she would take the job with 52 percent in the final vote, compared to 48 percent for the 51-year-old Sarkozy.

Far-right politician Jean-Marie Le Pen, who made it to the runoff vote in the 2002 presidential election, was credited with 15 percent of the votes, down one point.

Chirac, meanwhile, has not ruled out standing for a third term despite low popularity.

"I have been told that two sections of muscle had been removed in the thorax, and that the upper part of the left lung of the victim was missing," Schmit said.

"The absence of these body parts -- which have not been found at the scene of the crime -- make the suspect's confession of an act of cannibalism very probable."

The attack occurred Wednesday night in a detention centre in the northwestern city of Rouen.

The body of the 31-year-old victim, identified as Thierry Baudry, was found early Thursday when guards opened the cells.

According to the prosecutor, he had been beaten, cut with scissors and a razor, strangled and finally asphyxiated with a plastic bag.

A third detainee in the cell, a man aged 34, initially said he slept through the attack but later recanted. He, too, was facing murder charges and was to be questioned along with Cocaigne by an investigating magistrate Friday.

The prisons authority said the three men had requested to share the cell several days previously. It was not immediately known what motivated the attack.