British lawmaker Lucy Allan, who had said she would not stand in the national election, was suspended from the governing Conservative Party on Monday after endorsing the candidate for the right-wing Reform UK party.

This marks another setback for Prime Minister Rishi Sunak, who has been on the campaign trail since calling a general election last week. Dozens of Conservative lawmakers have already said they won't be standing in the July 4 election.

Allan, 59, who was the Conservative member of parliament (MP) for the English town of Telford and has been an MP for nine years, said on social media that she was supporting Reform's Alan Adams to be the constituency's next MP.

A Conservative Party spokesperson said she had been suspended from the party with "immediate effect," adding that "a vote for Reform is a vote for (opposition Labour leader) Keir Starmer."

A poll conducted by More in Common published a day after Sunak called the election on Wednesday showed 44 percent support for Labour and 27 percent for the Conservatives, with the right-wing Reform UK party at 10 percent.

Earlier this year, former Conservative Party Deputy Chairman Lee Anderson, who was suspended from the party over accusations of Islamophobia, defected to Reform, which has Brexit campaigner Nigel Farage as its honorary president. (Reuters)