Ms Le Pen and Mr Farage’s relationship dates back to when both were members of the European Parliament, and has had its ups and downs.

The two Eurosceptics hold tough views on immigration, and both have denied accusations that they are soft on Vladimir Putin. 

However, Ms Le Pen favours a more Left-wing and protectionist economic policy than Mr Farage. Her policies are grounded in cutting taxes, raising spending and borrowing heavily. In recent days, the party has rowed back on some of its more expensive plans in a bid to reassure markets.

Mr Farage, who has a longer history of backing free markets and low borrowing, has argued for significant spending cuts to try to shake up the Government’s finances.

In 2014, Mr Farage refused to form a European parliamentary alliance with Ms Le Pen when they were both MEPs because of her party’s “anti-Semitism and general prejudice”.

Ms Le Pen accused Mr Farage of “aggression” after European elections when both had led their Eurosceptic parties to victory. In a reference to his alleged roving eye, she suggested that the then Ukip leader had only formed an alliance with a rival party because its parliamentary assistants were prettier.

But writing in The Telegraph in 2017, Mr Farage praised Ms Le Pen for reshaping a party with roots “deep in Vichy” and with anti-Semitism “embedded in its DNA”. He said: “She is a sincere Eurosceptic,” added that her party was now “about sovereignty, not race”.

He backed her in her failed run at the French presidency that year, which included a now ditched campaign promise to hold a “Frexit” referendum.