Embattled UK leader Rishi Sunak suffered a fresh blow Monday when a former ally defected to a right-wing populist party that is worrying the ruling Conservatives ahead of this year's general election.

Lee Anderson announced that he was joining Reform UK, weeks after he was suspended from Sunak's Conservative party over comments widely condemned as racist and Islamophobic.

The 57-year-old former deputy chair of the Tories becomes the first MP to represent Reform, whose honorary president is arch-Eurosceptic and Brexit figurehead Nigel Farage.

The fringe party is currently polling at around 10 percent in opinion surveys, which if replicated at the election could split the right-wing vote in key constituencies.

That would make it even harder for the Tories, in power since 2010, to fend off a resurgent main opposition Labour party which is currently soaring ahead in national polls.

To blunt Reform's impact, Sunak could take his party further rightwards, continuing a trend in recent decades that has accelerated following the 2016 referendum on leaving the European Union.

Doing so risks alienating more socially liberal voters, however.

Anderson is an MP in a so-called "Red Wall" seat of working-class voters in northern England that are crucial to both the Conservatives and Labour's chances of winning the election.

Reform rails against immigration, net-zero energy policies and overbearing "nanny state" government regulations, and its members regularly heap praise on former US president Donald Trump.

"I want my country back," Anderson told reporters in London as he announced his defection.

He had been widely tipped to join Reform after he was suspended from the parliamentary party of the Conservatives in February for refusing to apologise for saying London's Labour mayor Sadiq Khan was controlled by Islamists.

Sunak has yet to announce the date of the election but has said it will be held in the second half of the year.