Embattled French conservative candidate Francois Fillon said today "no one" could stop him standing in the presidential election despite calls from within his own party to quit over an expenses scandal.

"No one today can prevent me being a candidate," Mr Fillon said in a TV interview in which he again said a probe into allegations he gave his wife a highly paid fake parliamentary job was politically motivated.

"Of course it is aimed at stopping me being a candidate," Mr Fillon said of the probe in which he is to be charged on 15 March.

Asked if he would bow to calls from within his own Republicans party to withdraw, Mr Fillon said: "My answer is no."

Earlier, Mr Fillon told supporters to "never give up the fight" at a campaign rally in Paris.

Mr Fillon told the rain-drenched crowd he had been "attacked by everyone" in the campaign.

With British-born Penelope watching him on the stage at the Trocadero opposite the Eiffel Tower, Mr Fillon admitted he had made "mistakes" and that he bore some responsibility if his campaign "was confronted by such formidable obstacles".

He apologised to his supporters, saying that among the judicial investigation "you have been forgotten" but the 63-year-old said he was confident he would be proved innocent.

Francois Fillon rally
Supporters, holding French flags, gather for a rally in support of Francois Fillon in Paris

Some lawmakers in Mr Fillon's Republicans party have called for a change of candidate, with the first round of the election fast approaching on 23 April.

Former prime minister Alain Juppe, 71, has indicated through his entourage that he could be ready to step in.

Mr Juppe is due to make a statement to the press in the morning.

Mr Fillon beat Mr Juppe in the right-wing nominating contest in November.

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The danger for the Republicans party is that an election that they once expected to win handily could slip away if Mr Fillon remains in place.

Polls currently show he would be eliminated in the first round, leaving far-right leader Marine Le Pen and 39-year-old centrist Emmanuel Macron to contest the May 7 runoff.

Meanwhile, a senior politician from Mr Fillon's conservative camp said that several party heavyweights were about to issue a statement calling for former prime minister Mr Juppe to replace him.

He is under growing pressure as party leaders prepare a crisis meeting for tomorrow to discuss the situation ahead of a 17 March deadline when all presidential candidates must be formally endorsed by at least 500 elected officials.