Labour trailed behind all rival parties to take last place in a Cornwall by-election in yet another blow to Sir Keir Starmer's Government. Lyndon Harrison, of Reform UK, held onto the Newquay Porth and Tretherras seat on Cornwall Council with 645 votes, following the death of previous councillor for the area Kevin Towill. He managed to see off the Green Party, which came second with 529 votes, an Independent candidate, with 361, and the Liberal Democrats, with 349.

In a clear sign that politics has broadened from the traditional two party system, both the Conservatives and Labour received significantly lower results, with Tory candidate Oli Kimber winning 132 and Labour's Suzanne Featherstone on just 120. Reform UK's successful defence came just months after it also managed to hold onto the seat for St Column Minor and Colan in December, further cementing it as the largest party on the southwest England council.

The results will likely cause concern among Labour members, coming just weeks ahead of the May local elections and following yet another Reform by-election victory in Salford, marking its first seat on the council this week.

It comes after new polling predicted that Reform UK and the Green Party could be set for major gains in London on May 7, including in Labour-held authorities like Barking and Dagenham.

YouGov said Labour could lose six councils next month, while Reform and the Greens gain three and four respectively.

Downing Street was also forced to insist Sir Keir Starmer will still be Prime Minister beyond the current Parliament on Friday after he faced calls to resign amid the fallout from the Peter Mandelson vetting scandal.

Sir Keir's official spokesperson said: "He's very focused on the job. I refer you back to his previous language that he will continue to lead the Government throughout this Parliament and beyond.

"He's got a huge amount of work to do. We're in the middle of a global conflict, the like of which we've not seen for years."

Adding to pressure on the Prime Minister, the leader of a group of backbench MPs said on Thursday that Sir Keir had made the "biggest mistake of his life" by appointing Mandelson as British ambassador to the US.

Jo White, who chairs the Red Wall group of Labour MPs, said the Government must "cleanse" itself of the problems that have emerged from the vetting scandal, for which former Foreign Office chief Sir Olly Robins was sacked last week.