Francois Fillon has already been charged in the case involving allegedly fictitious jobs as a parliamentary aide for which his Welsh-born wife Penelope was paid hundreds of thousands of euros.

The charges in the scandal dubbed "Penelopegate" also relate to a job she had at a literary magazine owned by a billionaire friend of the couple for which she allegedly did little or no actual work.

The new blow to the campaign comes less than four weeks before French voters go to the polls in a two-stage election on April 23 and May 7.