Andy Burnham swept to victory in a by-election which could send him to Downing Street as Britain's next prime minister.He said Labour had a “final chance to change” after his decisive win in Makerfield, setting up a showdown with Keir Starmer.Allies of Mr Burnham called on the Prime Minister to hand over power after the 'King of the North' defied national trends to increase Labour’s share of the vote in a seat where Nigel Farage’s Reform UK made sweeping gains in last month’s local elections.Mr Starmer has insisted he will not step down and will fight any leadership challenge. At the G7 summit in France this week, he said he wanted Mr Burnham to play a "big part" in Government. Mr Starmer will likely have only days to consider whether to resign and allow a “coronation” or face a potential cabinet revolt when Mr Burnham makes his move.Mr Burnham defeated Reform UK’s Robert Kenyon by 9,231 votes, up from 5,399 in 2024, and Labour’s vote share increased by 9.61 per cent.In his victory speech he urged his party to act now, saying there would be no second chance.He said: “Everyone knows that politics isn’t working.“Everyone can feel that the country isn’t where it should be. Tonight could, just could, be the turning point.”In a direct message to Labour MPs he said: “I do say to my own party: this is a final chance to change.“This is what people said directly to me on the hundreds of doorsteps that I stood on. We must hear it, we must act upon it and we must get it right. There will be no second chance.”Mr Burnham gave up the Greater Manchester mayoralty by becoming Makerfield MP, winning the seat that was vacated by Josh Simons in order to allow him the chance of returning to Westminster and seek to become prime minister.In an attempt at addressing the assertion that he was only seeking to become Makerfield’s MP to further his own ambitions, he said: “It will never be a stepping stone to me, but instead will be my touchstone.“A Makerfield test at the heart of British politics will make sure that the places Westminster has neglected will now get fairness.”Newly elected Makerfield MP Andy Burnham greets a supporter following his victory in the Makerfield by-election. ReutersInfoDecisive winMr Burnham won more than half of all votes cast, comfortably beating the combined total for second and third place parties Reform UK and Restore Britain.He won 54.8 per cent of the votes cast, outperforming all the opinion polls published during the campaign, none of which placed him above 50 per cent.Reform candidate Rob Kenyon won 34.5 per cent of the vote, while Restore Britain’s Rebecca Shepherd won 6.8 per cent, which together come to 41.3 per cent.Ms Shepherd was the only other candidate to get more than 5 per cent of the votes cast – the threshold needed to avoid losing the £500 deposit that all candidates have to pay to stand for election to parliament in the UK.The Conservatives, Liberal Democrats and Greens, along with eight other candidates, all got less than 5 per cent of the vote and lost their deposit.Cabinet minister Lisa Nandy said she wanted Mr Burnham “back at the top table”.The Culture Secretary said: “What Andy’s shown here is that there is something that he brings, a willingness to go out and fight for the change that people need, to take on any system and any person who stands in the way and to be bold and to wear his heart on his sleeve, and people have responded.“I think that with him back in the top team, at the top table, helping to drive that change, I think we’ll be in a really strong position.”Leadership challengeMr Burnham has indicated he will not accept a job in Mr Starmer’s Government.He is not expected to launch a leadership challenge immediately, instead hoping Mr Starmer will conclude that he has to give up the keys to No 10.Mr Burnham’s supporters believe the scale of his victory will put increased pressure on Mr Starmer to stand down.Former cabinet minister Louise Haigh urged the Prime Minister to set out an “orderly and managed transition” of power.She told the BBC she hoped Mr Starmer will “do what’s best for both the country and the Labour Party”.But the Prime Minister has repeatedly insisted he has no intention of walking away from No 10 and is understood to have amassed a war chest to fund his campaign to fight any leadership challenge.He has the backing of a group of private donors, with fundraising having ramped up in the last two days and total pledges running into six figures, sources said.Mr Burnham has indicated he would join a leadership contest if one was triggered, something that would require 81 MPs to line up behind a candidate.Former health secretary Wes Streeting has suggested he would be willing to fire the starting gun for a contest if Sir Keir does not stand down.Polling expert Sir John Curtice said Mr Burnham’s victory was not likely to lead to a nationwide surge in Labour’s popularity.Speaking on the BBC, he said: “Can this be replicated elsewhere? First thing to note, between them the Conservatives, the Greens and the Liberal Democrats got no more than 3 per cent of the vote.“I think one has to say that there are two crucial elements to Mr Burnham’s success. The first is the apparent readiness of those who are minded to vote for parties other than Reform, or indeed Restore Britain, their readiness to fall in and vote for Mr Burnham.“The second element of Mr Burnham’s success is that in a sense he was riding two horses at once. He was both riding as the person who was trying to appeal to the traditional Labour vote … and he was also able to appeal to those who wanted to see the back of Keir Starmer.“The question you have to ask yourself is when Mr Burnham becomes prime minister, how easy will that trick be to repeat? Because once he’s his own man, he’s not going to be able to campaign against himself in the way he’s campaigned against Keir Starmer."In the other Westminster by-election results the Tories secured victory in Aberdeen South, with Douglas Lumsden taking the seat vacated by the SNP’s former Westminster leader Stephen Flynn, who won election to the Scottish Parliament in May.In Arbroath and Broughty Ferry the SNP’s Lara Bird held the seat vacated when Stephen Gethins became an MSP.