An Ipsos-Sopra Steria poll on Wednesday placed him in third place in Sunday’s first round on 16 per cent but approaching Marine Le Pen, on 21.5 per cent, with Mr Macron in front on 26.5 per cent.

Encouragingly for the volcanic contender, the poll found that 55 per of French were “discontented” and 37 per cent felt close to “angry and very anti-establishment France”.

With Socialist candidate Anne Hidalgo now on two per cent in round one and Green contender Yannick Jadot sputtering on around six per cent, the France Unbowed leader cast himself as alone in being able unite ecologists and Left-wingers, beseeching them to vote tactically in his favour.

He also held out an olive branch to “yellow vests” and would-be Le Pen voters he called “fachés mais pas fachos” (angry but not fascists), asking them: “What would it serve to bring this woman to power?”

While she has based much of her campaign on promises to improve the purchasing power of the French, Mr Mélenchon insisted his more radical measure of “blocking fuel prices” would go much further.

“She puts on a snooty air and says she wants to give money back to the French. Sorry, what are you talking about?,” he asked.

Mr Mélenchon has pledged to lower the retirement age from 62 to 60 while bringing back a disbanded wealth tax and launching a massive €200 billion green investment plan. 

“We have no time to lose,” he said of the climate crisis, promising to use “all human, intellectual, financial, social and cultural means” to honour the 2015 Paris climate agreement

He also appealed to progressive values, saying a “feminist revolution” was under way and called for a Sixth Republic, handing more power to parliament and reducing presidential powers.