French President Nicolas Sarkozy said he was the man to defend a “strong France” as he announced his re-election bid with 10 weeks to the vote and his Socialist rival leading inopinion polls.

Portraying himself as a tough realist as France faces crises “unknown since World War II” and dismissing front runner François Hollande as a dreamer, Mr Sarkozy said he felt it was his duty to seek a new five-year term.

“Yes, I am a candidate in the presidential election,” Mr Sarkozy said in an interview on France’s TF1 television.

“I took this decision because France, Europe and the world have for the last three years seen a series of unprecedented crises.

Not seeking a new mandate from the French people would be abandoning my duties.”

Mr Sarkozy presented himself as “the captain of a boat in the heart of a storm” and promised: “The French people must understand that if France is strong, they will be protected. France is a shield for each of us.”

Mr Sarkozy slammed Mr Hollande’s left-wing campaign programme, which promises significant state spending and the creation of thousands of teaching jobs.

“Do you really believe that in the current economic climate we can tell the French people that we do not need to save? In my long political career I have seen many people promise a dream.

“Those dreams always turned into nightmares,” he said, directly attacking Mr Hollande’s pledge to revive “the French dream”.

Mr Hollande had pre-empted Mr Sarkozy’s declaration by staging a massive campaign rally in his home town in Rouen, televised live just minutes before the President’s interview. He lashed out at Mr Sarkozy’s record.

“The script has been written: the incumbent candidate will promise new things. He will try to turn his weaknesses into strengths. He has been wrong for five years and now he calls that experience,” Mr Hollande said.

“He’ll pretend that a diet of austerity is a 21st-century solution, that we must forget his record, that the crisis has passed, everything is forgotten, that only the future counts,” Mr Hollande said.

Mr Sarkozy, 57, has been operating on a de facto campaign schedule of television appearances and twice-weekly regional tours for months now, but had yet to officially confirm his candidacy.

Opinion polls consistently forecast that Mr Sarkozy will be beaten by Mr Hollande in a run-off on May 6, but the President’s camp is clinging to hope that he can rekindle the energy that brought him to office in 2007.

Mr Sarkozy’s programme combines the most modern tactics – he launched a Twitter account on Wednesday – with the most traditional – he visited a provincial cheese factory in the Alps yesterday.

The French left has not won a presidential election since 1988, but former Socialist Party leader Mr Hollande, 57, has a comfortable lead in the surveys of likely voters.

The latest poll published by Harris Interactive for the news magazine VSD forecast that Mr Hollande would win the first round with 28 per cent to Mr Sarkozy’s 24 per cent, then sweep the run-off with 57 per cent to 43.

In this poll the only other candidate within striking distance of the second round would be far-right National Front leader Marine Le Pen on 20 per cent, but most observers now see the campaign as a two-horse race.

Brandishing a red card like a football referee expelling a player, Ms Le Pen urged her supporters to teach Mr Sarkozy a lesson at the polls.

“There have been too many betrayals, too many lies, too much manipulation, Nicolas Sarkozy must leave the pitch and give way for a bold, enthusiastic, courageous and clear-headed team, mine!” Ms Le Pen said.

Mr Sarkozy began his time in office vowing to liberalise the economy, reduce unemployment and increase voters’ spending power but has instead seen France fall prey to the eurozone debt crisis. He did have some good news: economic growth in the final quarter of last year was confirmed as having been slightly higher than first thought, and thus France is not officially in recession.

But in an interview last week, Mr Sarkozy focused on a conservative social platform rather than on the economy, with plans to ban gay marriage and adoption, limit immigration and restrict unemployment benefits.