France's right-wing presidential candidate Francois Fillon has been charged with several offences over a fake jobs scandal that has seriously damaged his chances of winning April's closely contested election.

His lawyer Antonin Levy told AFP news agency on Tuesday that Fillon was charged with misuse of public funds and misuse of corporate assets.

The charges stem from an investigation his wife and children were paid hundreds of thousands of dollars of taxpayer money for work they did not actually perform.

Following an investigation by the weekly newspaper Canard Enchaine, the 63-year-old presidential candidate admitted in January to employing his wife, Penelope, and two of their children as parliamentary assistants.

Penelope earned about 680,000 euros ($730,600) between 1986 and 2013 while working as a legislative staff member.

Despite the scandal causing a deep rift within his The Republicans party, Fillon has vowed to continue, calling the investigation an attempted "political assassination".

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Once a frontrunner, Fillon has seen his popularity drop following successive waves of revelations in French newspapers.

The allegations over the allegedly illusory jobs have been particularly damaging to his campaign because Fillon used to tout his reputation for probity.

Independent centrist candidate Emmanuel Macron has since overtaken Fillion in pre-election polls, increasingly appearing as the new frontrunner.

Polls suggest Macron will beat Marine Le Pen in the decisive second round on May 7 - but after Donald Trump's victory in the United States and Britain's vote to leave the European Union, analysts caution against predictions.