Centrist candidate will address more than 3,000 French people in Central Hall hoping to persuade those registered to vote abroad

More than 3,000 French voters are set to pack out Central Hall in Westminster on Tuesday as Emmanuel Macron, the centrist outsider seen as a leading contender in France’s presidential race, brings his campaign to London.

With nine weeks to go before the first round of a wide-open contest, the former investment banker and economy minister is seeking votes where he can find them and hoping his crusade to break the “complacency and vacuity” of a failing French political system will find favour with expatriates.

Renaud Auffret, 36, a software engineer, said: “He’s certainly an interesting guy. He’s energetic, he wants to shake things up. Economically on the right, socially on the left; for lots of the kind of French people here, he sounds like good news.”

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An opinion poll on Monday put the far-right candidate Marine Le Pen seven points clear of Macron and his conservative rival François Fillon, who are tied on 20%, in the first round. But Le Pen, the Front National leader, would lose to Macron and Fillon in the 7 May run-off, the poll predicted, by margins of 16 and 12 points respectively.

Facing mounting calls to turn his impassioned campaign rhetoric into hard policies, Macron, 39, will seek, and could find, votes in London’s French community, estimated at 300,000 people, many of them relatively young, globally minded and in principle open to his message.

Those registered to vote abroad can cast their ballot in the presidential poll and, as members of France’s northern Europe parliamentary constituency, the general election that will follow in June.

Noémie Delmas, a human resources consultant who has lived in London since 2008, said: “Nobody who is not the candidate of a party has ever become president, so we must be careful. But perhaps that’s what France needs now; someone without the old ideologies, with new ideas, from outside politics.”

Armed with a well-filled contacts book from his days as a Rothschild’s dealmaker, Macron has successfully raised several million euros in campaign funds from dinners and invitation-only meetings with expats in London, Brussels, Berlin, New York and Silicon Valley, at which guests are invited to contribute as much as €7,500 (£6,400) to the cause.

The latest poll suggested his support had softened somewhat after a weekend in which the electoral novice, who has never stood for office but is pulling in crowds with his youthful En Marche! (Forwards) grassroots movement, was criticised for comments he made during a visit to Algeria last week that France’s colonial past could be considered “a crime against humanity”.

Support for Le Pen’s hardline anti-immigration and law and order policies, meanwhile, appears to have hardened marginally amid continuing weekend violence in France’s troubled banlieues, following the alleged rape of a 22-year-old man during a violent police arrest.

Macron said he was sorry if he had hurt French citizens who fled Algeria when it became independent in 1962, but did not withdraw his remark and urged people to move on. Supporters of his rivals, however, turned their fire on the independent candidate for his inexperience and lack of a concrete programme.

Valérie Pécresse, the president of the Ile-de-France region that includes Paris, and a Fillon supporter, said Macron did not have the solidity to advance to the second round of the election, let alone the stature to be head of state. “He tells people what they want to hear,” she said. “That won’t cut it against Trump or Putin.”

Another Fillon backer, the former budget minister Éric Woerth, told RTL radio that Macron, who says he is “of the left” but open to ideas from the right, was nothing more than a “television evangelist ... all about seduction, and not at all about conviction. His project changes according to the last expert he spoke to”.

Denouncing “shocking remarks … that can only revive tensions”, Florian Philippot, Le Pen’s closest adviser, told LCI television that Macron was a candidate “without a programme … at the beck and call of the banks: the globalisation candidate”.

Fillon has been wounded by claims that he paid his wife and children as much as €1m of public money for parliamentary assistance, which investigators suspect was never provided. Promising not to step down even if placed under formal investigation, he released a Facebook video urging his voters not to be “intimidated by attacks”.