Keir Starmer believes Nigel Farage's Reform UK are the "main opposition"

Keir Starmer has ordered his party to focus its sights on Reform UK because they are the "main opposition" not the Conservatives. The Prime Minister believes that Nigel Farage's right-wingers are the biggest threat to him being turfed out of No 10.

And Sir Keir is willing to face-off against the Brexit architect in a live head-to-head TV debate before the next general election. Reform's victory in the Runcorn and Helsby by-election combined with its surging poll ratings has triggered the sudden change of attack, even though they only have five MPs.

A senior Labour source said: "The Tories are over, Reform is now the real opposition."

The Daily Express understands that the Prime Minister regards Mr Farage as a more popular leader with the public than Kemi Badenoch.

Last night the Reform UK leader said: "I accept his offer!"

Sir Keir repeatedly turned his guns on the Reform leader during this week's Prime Minister's Questions in a clear sign that his tactics are changing.

And in fierce exchanges with Mrs Badenoch he said the Tory party is sliding into "brain-dead oblivion" before branding them a "dead party walking".

The source added: "The old two-party politics is over and Reform is on the rise".

Sir Keir has toughened up his rhetoric in recent days, notably during a speech on immigration which drew awkward comparisons to language used by Enoch Powell.

His "island of strangers" remark and other elements of the speech were widely interpreted as a desperate attempt to pitch to the right.

But they also drew criticism from a number of Labour backbenchers.

Labour strategists are expected to turn their guns on Reform's policy aims and how the party would fund public services like the NHS.

Reform's rapid rise has seen party top polls for months with voting experts predicting they could even sweep to power at the next election.

Mr Farage declared his party the "main opposition" after Sarah Pochin dramatically snatched the safe Labour seat by six votes in this month's by-election.

Reform also won two mayoralties, including former Tory MP Andrea Jenkyns, and a number of local councils in a stunning set of results which saw them secure 41% of the seats up for grabs.

Following the results polling expert professor Sir John Curtice said the Conservative and Labour's joint dominance of British politics could be over.

"We certainly cannot rule out the possibility that this proves to be the case," he said.