Wife TV clip poses new problems for France's Fillon

French presidential candidate Francois Fillon was fighting to keep his campaign alive yesterday as a TV interview with his wife added fuel to fake job claims and some members of his party openly plotted to replace him.

One of France's main investigative news programmes, Envoye Special, is set to air previously unseen footage of Fillon's British-born wife Penelope talking to a journalist in 2007.

Envoye Special presenter Elise Lucet told AFP that "several interesting phrases" had been found in the long-forgotten interview, including that she had never been her husband's parliamentary assistant.

The British journalist who did the text version of the interview for the Sunday Telegraph newspaper, Kim Willsher, told AFP she did not recall the phrase in question and that she had never seen the complete video.

The interview was "not a political interview, it was a 'wife of' piece," she said.

Fillon had been leading the presidential race until allegations emerged in the Canard Enchaine newspaper that his wife earned a pre-tax income of 830,000 euros ($900,000) as a parliamentary assistant over more than a decade -- despite no-one recalling her ever working at the National Assembly.

A poll on Wednesday showed Fillon would crash out in the first round in April behind far-right leader Marine Le Pen and 39-year-old centrist Emmanuel Macron, who is rising fast in the polls.

Facing a judicial investigation over his wife's supposed role, 62-year-old Fillon has flatly denied the accusations and insists the previously low-profile Penelope worked for him.

Two of the couple's children were also employed as his parliamentary assistant at one point, earning an additional 84,000 euros before tax.