Andy Burnham has triumphed over Reform and won the Makerfield by-election, securing his return to Westminster and setting up a widely expected challenge to Sir Keir Starmer’s leadership. The Greater Manchester mayor won by a sizeable 9,231 votes, comfortably seeing off the challenge from Nigel Farage’s Reform UK.Mr Burnham’s victory sets up a potential leadership contest unless the Prime Minister agrees to step down.Follow reaction from the Makerfield by-election hereIn his victory speech he said Labour had a “final chance to change” and “we must act upon it”.Sir Keir has insisted he will fight any attempt to challenge him and has been building up a war chest for a leadership campaign.Labour party candidate Andy Burnham is declared the winner of the Makerfield by-election (PA)But Mr Burnham’s supporters urged the prime minister to set out an “orderly and managed transition” of power.Former cabinet minister Louise Haigh, who has been close to the Burnham by-election campaign, said she hoped Sir Keir will “do what’s best for both the country and the Labour Party”.Mr Burnham increased Labour’s majority in a seat which voted for Reform in council elections last month, achieving a positive swing of over 3 per cent.Following his decisive victory 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.”Sir Keir Starmer (seen here at the G7 in France this week) has insisted he will fight any attempt to challenge him (PA Wire)He added: “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.”At the count earlier, culture secretary Lisa Nandy said that Mr Burnham deserved to be heard “loud and clear at the top of politics” after his successful campaign.She later called the result “history in the making”. She 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.”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.”Wes Streeting, also an ex-health secretary, says if Mr Burnham stands against Sir Keir, he will join the contest.