France's financial prosecutor on Thursday said its investigations into fake work allegations surrounding presidential candidate Francois Fillon and his wife Penelope would continue.

In a statement, the prosecutor said that "numerous elements collected (by investigators) do not, at this stage, permit the case to be dropped."

A three week-old scandal over hundreds of thousands of euros in taxpayers' money which conservative Fillon's wife was paid for work she may not have done has cost the 62-year-old former prime minister his status as favourite to win the French presidency in May.