The gun of a Lebanese jeweller and the explosive words of a former Prime Minister have given a double boost to the surging electoral prospects of the French far-right leader Marine Le Pen.

A Facebook page, set up in support of a jeweller accused of manslaughter after he shot dead an armed robber, broke French-language records for an online petition at the weekend.

By Sunday night, something approaching two million people had registered their support for Lebanese-born Stéphane Turk, 67, who shot and killed a 19-year-old alleged robber in Nice last Wednesday.

Download the new Independent Premium app Sharing the full story, not just the headlines

The online support for Mr Turk was launched by extreme nationalists close to Ms Le Pen’s National Front (NF) and supported by both her and her father, and predecessor, Jean-Marie, at the party’s “summer university” event in Marseille at the weekend.

Mr Turk’s popularity is reminiscent of the Norfolk farmer, Tony Martin, who became a hero to the right wing in Britain after he was jailed for killing a burglar in 1999.

The French jeweller claims he acted in self-defence. The public prosecutor says he shot the robber in the back as he was riding away on the pillion seat of a motorcycle.

At the same time, the traditional French right has been thrown into angry confusion by the comments of the former Prime Minister François Fillon, apparently inviting moderate electors to transfer their second-round of votes to the National Front in municipal elections next spring.

Mr Fillon said that in second-round contests where the centre-right candidate had been eliminated, UMP voters should choose the “least-sectarian” candidate, whether from the NF or the left wing. This was a clear break with party policy which urges voters to support neither. Mr Fillon, a declared presidential candidate for 2017, was accused by senior colleagues yesterday of “crossing a fault line” and “handing a step-ladder” to the NF.

Ms Le Pen, relishing her domination of the political debate, said that the UMP – the party of former presidents Jacques Chirac and Nicolas Sarkozy – was now a “black hole” which was “imploding, but imploding weakly”.

Opinion polls published yesterday showed sharply rising support for her and the extreme nationalist party she has tried to reform and “de-demonise” since succeeding her father as leader in 2011. A BVA poll for Le Parisien suggested that 34 per cent of people now had a “good opinion” of Ms Le Pen and 31 per cent would consider voting for her. On the other hand, the same poll pointed to strong, continuing resistance to the NF and to Ms Le Pen. More than 67 per cent said they would never consider voting for her in any circumstances.

Nonetheless, pollsters and political commentators said that the rise in Ms Le Pen’s popularity, and the viral support for the jeweller arrested in Nice, pointed to possible record gains for the NF in next year’s municipal and European elections.

Boosted by the unpopularity of both the centre-left government and the centre-right opposition, high unemployment and fears of crime, the NF hopes to win 1,000 council seats and a string of mayorships in south-eastern and north-eastern France in March.