Keir Starmer's political future is on the line today in a historic round of local elections.

Millions of voters across England, Scotland and Wales will head to the polls for what opposition leaders have branded a referendum on the Prime Minister's record.

His Labour rivals are waiting in the wings, ready to pounce if predictions of a meltdown across the country become reality. The elections threaten to shake the foundations of Britain's two-party system, with voters set to vent their anger with Labour and the Conservatives by backing Reform UK and the Greens in large numbers.

Kemi Badenoch said today's vote would show 'what multi-party politics looks like' – but warned that voters shunning her Tory party were taking a gamble by installing untested politicians to run key services.

'The two-party era has moved into a multi-party era,' she said. 'But the fact is none of these new parties or Labour have a plan for the country. What's astonishing is that a Labour government that came in less than two years ago on a landslide has become so unpopular. They thought governing was easy. It is not.'

Polls suggest Labour could suffer its worst ever round of local elections, losing more than 1,500 council seats in England and battling to avoid coming third in Scotland and Wales.

Nigel Farage last night predicted sweeping gains for Reform UK against Labour and the Conservatives.

Speaking at a campaign rally in St Helens, Merseyside, he said Labour would be 'wiped out' in Red Wall areas in the North and the Midlands – and that the Tories would 'no longer be a national party'.

'The implications of this vote will be historic,' he said. 'In Labour's traditional heartlands they are going to get a drubbing of the likes they have not had for well over a century.'

With the Greens poised to make inroads in Labour strongholds in London and the inner cities, and nationalist parties expected to prosper in Wales and Scotland, a Labour insider acknowledged the party was in danger of 'losing to everyone, everywhere.'

Downing Street is braced for a potential challenge to the PM's leadership within hours of the polls closing tonight, with a Cabinet minister last night pushing for a return to Westminster for Manchester mayor Andy Burnham. Allies of the PM insist he will not make way and are already preparing for a fight.

But senior Labour figures have warned the local election campaign has hardened opinion against him, with voters singling him out for criticism on the doorstep. One Red Wall Labour MP told the Mail: 'We are going to lose every seat locally to Reform. Good councillors are going to lose their seats and a lot of it is down to the PM.

'The response on the doorstep to him personally is dire – people detest him. It is obvious that he can't lead us into another election. He is radioactive with the public – It is just unsustainable.'

Welsh Labour leader Eluned Morgan yesterday warned there was a danger that the PM's unpopularity could see the party lose power in the country. It has emerged as Wales's biggest party at every election since 1922. Ms Morgan acknowledged that Sir Keir 'comes up as an issue on the doorstep' and pleaded with voters to focus on Welsh issues rather than 'picking a fight' with the PM.

Sir Keir has fought a low-key campaign and made only a few controlled visits. Yesterday he manned a phone bank in Labour HQ rather than knocking on doors where he might come face-to-face with angry voters.

In an eve of election message, the PM urged voters to 'choose unity over division', saying that Mr Farage and Green Party leader Zack Polanski had shown they were 'not fit to meet this moment of great global instability'. Former deputy PM Angela Rayner and Health Secretary Wes Streeting are both said to be weighing up a leadership challenge if the results of today's vote are worse than expected.

Downing Street is also determined to resist any attempt to allow Mr Burnham to return to Westminster where he could launch a leadership challenge.

The Mail revealed yesterday that preparations are in place for a sympathetic North West Labour MP to step aside as soon as next week to open up a route back to parliament for the Greater Manchester mayor.

Several cabinet ministers are ready to tell Sir Keir that the price of their support is a guarantee that Mr Burnham is not blocked from running for a seat again.

Sir Keir last night wrote to all civil servants in a bid to build bridges after his sacking of former Foreign Office chief Sir Olly Robbins over the Peter Mandelson scandal. He insisted he valued officials who 'speak truth to power'.

A YouGov poll in Wales suggested Labour is set to come in third with 12 per cent of the vote, far behind Plaid Cymru on 33 and Reform on 29.

A similar survey in Scotland suggested the SNP are likely to be just short of a majority, with Labour pushed into third behind Reform.

Labour has focused its recent campaign on London where inner city strongholds look vulnerable to a surge by the Greens. Campaigners were last night clinging to the hope that the Greens' performance may be dented by controversy surrounding Mr Polanski, who questioned the force used by police when detaining a man who stabbed two Jewish people in Golders Green last week.