Nigel Farage, the colourful politician who helped champion Britain's departure from the European Union, said on Monday he would stand as a candidate in next month's election and will lead the Reform Party in a blow to Prime Minister Rishi Sunak.

The decision by Farage, now a TV host and previously honorary president of Reform, will boost his movement's profile and challenge Sunak's governing Conservatives for the support of right-leaning voters.

Farage, 60, had previously said he would not stand in the July 4 vote in order to help his friend Donald Trump fight the US election later this year.

"I’ve decided I’ve changed my mind," Farage told a news conference. "It’s not always a sign of weakness, it could potentially be a sign of strength."

Farage has stood unsuccessfully for parliament seven times but is still one of the most influential British politicians of his generation, putting pressure on a succession of prime ministers to take tougher positions on Europe and immigration.

At the last general election in 2019, Farage's party decided not to contest seats held by the Conservatives, then led by Boris Johnson, to avoid splitting the pro-Brexit vote.

Polls suggest the opposition Labour Party is on course for victory this time, with the Conservatives staring at one of the worst results in their history.

Support for Reform runs at about 10 percent nationally, giving the party the third highest vote share, polls show.

But under Britain's winner-takes-all system, the party had not been expected to win any seats. (Reuters)