Sir Keir Starmer tonight defiantly vowed to lead Labour into the next general election amid growing speculation about a leadership challenge from Andy Burnham.The Prime Minister dismissed the 'personal ambitions' of the Greater Manchester mayor as he also swiped at Mr Burnham's economic agenda.Speaking to regional broadcasters on the eve of Labour's annual conference in Liverpool this weekend, Sir Keir said his political project was a '10-year' endeavour.He also defended the Government's record a year into office in a series of interviews, despite having recently suffered a slew of major setbacks.Sir Keir said he was 'proud' of what Labour had achieved since their landslide election victory last July and refused to 'get drawn into' reports of plots against him.It came after Mr Burnham triggered a major bout of Labour infighting by claiming mutinous MPs want him to challenge Sir Keir for the party leadership.The Greater Manchester mayor was told in no uncertain terms by allies of Sir Keir to stay up North and do his job after he lashed out at the PM.Mr Burnham, who twice failed to be elected Labour leader when he was an MP, accused Sir Keir of leaving the party riven by 'alienation and demoralisation' since entering No10. Sir Keir Starmer defiantly vowed to lead Labour into the next general election amid growing speculation about a leadership challenge from Andy Burnham The Prime Minister dismissed the 'personal ambitions' of the Greater Manchester mayor as he also swiped at Mr Burnham's economic agenda Mr Burnham said he had been approached by MPs who wanted him to mount a leadership challenge and outlined his own tax-and-spend manifesto that included £40billion of borrowing to fund housebuilding.Speaking to BBC North West on Thursday, Sir Keir said: 'I'm not going to get drawn in to commenting on the personal ambitions of the mayor.'But I do want to be really clear about our fiscal rules because economic stability is the foundation stone of this Government.'It was three years this week ago that we had the Liz Truss experiment where she abandoned fiscal rules, in her case for tax cuts, and the result was a disaster for working people.'The same would be true if you abandoned fiscal rules in favour of spending. And I'm not prepared to ever have that inflicted on working people again.'The PM told ITV Anglia he had defied those who doubted he could change the Labour Party, 'they said, you can't win an election in 2024 – I said yes we can, and we did with a landslide victory'.'Now people (who) are saying to me you can't change the country (are) getting the same answer. We can and we will,' he added.Asked whether he could guarantee he would lead Labour into the next general election, scheduled for 2029, Sir Keir said: 'Yes.'I've been very clear that this is a project of national renewal – patriotic national renewal – I was clear about that when we launched the campaign, as we did last year.'I'm very clear that that is a 10-year project. I led from the front into the last election, I'll lead from the front into the next election.'Pressed on potential plots against him, Sir Keir told BBC West: 'I think all PMs have a degree of praise and criticism.'My job is not to get drawn into that. My job to fix the problems in this country.'Mr Burnham's comments had earlier also prompted a blunt response from Government ministers who pointed out his term as Greater Manchester mayor runs until 2028.Housing Secretary Steve Reed branded Mr Burnham a 'regional politician' and suggested he concentrate on the city - a point later echoed by Chancellor Rachel Reeves.'In the same way that this Government are (sic) delivering change, I know that Andy is focussed on delivering change in Greater Manchester,' she told broadcasters.Questions were also raised about Mr Burnham's claim that the UK has 'got to get beyond this thing of being in hock to the bond markets,' with comparisons drawn with Ms Truss's financially chaotic time in office as a Tory PM. Respected economist Paul Johnson said: 'The bond markets are simply the people and institutions who lend government money.'We can avoid being ''in hock'' to them by reducing borrowing.'We struggle now because our borrowing and debt are extremely high. Mr Burnham wants to increase borrowing.' 'In the same way that this Government are (sic) delivering change, I know that Andy is focussed on delivering change in Greater Manchester,' Rachel Reeves told broadcastersMr Burnham later took to the airwaves himself to insist he 'loved' his role in Greater Manchester and was committed to serving a full term as the region's mayor. He had used a newspaper interview ahead of Labour's annual conference to set out a massive tax-and-spend manifesto he claimed could 'turn the country around'.It would see the top rate of income tax hit 50 per cent and increase council tax on homes in the south of England, with £40billion of borrowing to nationalise housebuilding. But yet again he stopped short of confirming whether he would resign as mayor and seek a Westminster seat to take on the PM directly, which would require a by-election and support from 80 other MPs.He insisted to the Telegraph he was not 'plotting to get back', a view not universally shared. However MPs suggested he would find it hard to win a Westminster seat in the current climate, with one telling the Daily Mail: 'We all know he's not a fan of England south of the Keele services and hasn't ever really talked about Wales or Scotland so where he thinks his pathway lies with MPs would fascinate me.'And if anyone thinks any by-election right now is a cert for Labour then they are taking the voters for granted - the very thing people hate and (which) is turning them towards Reform et al.'And in a round of media interviews this morning, Mr Reed pointedly told Times Radio: 'He will keep doing that work (Manchester mayor), because that is the commitment he gave until the end of his term.'He's given a commitment. I'm sure he wouldn't break it.'And Labour backbencher Neil Coyle tweeted: 'The annual ''Burnham wants to be leader'' headlines just before conference are more grating this year. 'He didn't take on the guy who oversaw Labour's worst defeat in a century and facilitated anti-Semitism, but pops up now under a huge majority and with four years to go?! No ta. 'Another MP told the Huff Post: 'Keir should say to him ''any time you want Andy, there'll be a seat for you, and I want you in government''. 'He'd s**t himself. People would see how useless he is.'This afternoon, after the criticism, Mr Burnham appeared to row back from the idea he would quit as mayor, telling BBC Radio Manchester: 'I love everything about this job. I am completely committed to it … and I think what we've got to do is to sort of stop the sense in Westminster at times that everything is in flux.'He said he had not 'gone out there, just me on my own' and suggested 'people have been getting in touch with me' asking him to run.Mr Burnham had earlier set out his vision for how to 'turn the country around', saying there was a 'huge underpayment of tax that should now be corrected' in London and the South East because the rates were based on property valuations from 1991.The PM has had a bruising few weeks in which two high-profile Government departures and sustained lag behind Reform UK in the polls have sparked questions about his leadership.Mr Burnham, a former New Labour minister and ex-MP for Leigh, insisted he was not plotting an immediate return to the Commons or wanting to step on the Government's toes as it seeks a reset at the Labour Party conference.He signalled a willingness to work with the Liberal Democrats and Jeremy Corbyn, and told the Telegraph he believed Britain should introduce proportional representation to encourage co-operation within the 'progressive majority'.Asked if MPs had urged him to run for the top job, he said: 'People have contacted me throughout the summer – yeah.'I'm not going to say to you that that hasn't happened, but as I say, it's more a decision for those people than it is for me.'