French rock star Johnny Halliday's plans to leave the country have sparked a political row.
Hallyday made a failed bid to acquire Belgian nationality this year
The singer, who is a high-profile supporter of the centre-right interior minister Mr Sarkozy, is moving to Switzerland to escape French taxes.
Francois Hollande, leader of the rival Socialists, joked it was "a really nice way to support his chosen candidate".
Mr Sarkozy is the leading candidate to represent the ruling UMP Gaullist party in next year's presidential election.
Mr Hollande told French station Radio J: "If he really thought Nicolas Sarkozy could win, and was so convinced by his policies, he only had to wait four months."
And at a rally, left-wing candidate Segolene Royal said she had deliberately avoided "having as a friend someone who escapes to Switzerland to pay their taxes".
Hallyday, who has sold 100 million albums during a 40-year career, must spend six months and a day each year in Switzerland to avoid French taxes.
Mr Sarkozy says France should be a place for everybody, rich or poor
In September, he posed with Mr Sarkozy to support the politician's campaign, but warned he would leave France if Mr Sarkozy failed to keep his promises.
President Jacques Chirac, who presented Hallyday with the medal of knight in the Legion of Honour in 1997, said he valued Hallyday as a friend and an artist but regretted his actions as a citizen.
Mr Sarkozy has declined to comment directly.