The UK's health secretary has resigned from cabinet and another Labour MP has quit parliament paving the way for a potential leadership challenge to under-fire prime minister Sir Keir Starmer. UK cabinet minister Wes Streeting, who is widely viewed as a potential leadership candidate, quit his role as health secretary.His allies said he was preparing a tilt for the top job. Sir Keir, who won a landslide election less than two years ago, is facing growing calls to quit following catastrophic local election results last week which saw the Labour Party lose almost 1,500 local council seats to its opponents.UK Prime Minister Keir Starmer is under enormous pressure from within his party to quit. (Reuters: Toby Melville)"It is now clear that you will not lead the Labour Party into the next general election and that Labour MPs and Labour Unions want the debate about what comes next to be a battle of ideas, not of personalities or petty factionalism," Mr Streeting said in a letter to the prime minister published on X.He went on: "You have shown courage and statesmanship on the world stage — not least in keeping Britain out of the war in Iran. "But where we need vision, we have a vacuum. Where we need direction, we have drift."In a reply to Mr Streeting, the prime minister, said: "I am truly sorry you will no longer be sat at the cabinet table helping to transform our National Health Service. "As part of that we must deliver on all of the promises we made to the country, including our promise to turn the page on the chaos that was roundly rejected by the British people at the last general election."Another likely challenger, former deputy prime minister Angela Rayner, said on Thursday that she had reached an agreement with tax authorities to clear up questions about her taxes that forced her to leave the cabinet last September.While Mr Streeting comes from the moderate wing of the centre-left Labour Party, as does Sir Keir, Ms Rayner is a favourite of more left-wing voters, calling on the party to do more to boost the minimum wage and raise taxes on the rich.Ms Rayner told the Guardian newspaper that Sir Keir should "reflect on" his position, adding that she was ready to "play my part" in any leadership election if Mr Streeting were to trigger a contest.Former deputy prime minister Angela Rayner could launch her own bid for the Labour leadership. (Reuters: Chris J Ratcliffe)Labour MP Josh Simons also said he would also resign from his seat in parliament to allow Manchester Mayor Andy Burnham, who has been seen as a potential challenger to Sir Keir, to stand. "I am standing aside so that Andy Burnham can return to his home," Mr Simons said. "We have lost the trust of those our party was built to serve. It is my unwavering belief that nothing short of urgent, radical, courageous reform will make a difference."Manchester Mayor Andy Burnham outside Downing Street in March. (Reuters: Justin Tallis)Mr Burnham said he would now request permission from the party's ruling body to stand in the by-election in the region."There is only so much that can be done from Greater Manchester," he posted on X. "Much bigger change is needed at a national level if everyday life is to be made more affordable again."This is why I now seek people’s support to return to Parliament: to bring the change we have brought to Greater Manchester to the whole of the UK and make politics work properly for people."Allies had previously suggested a sitting member of the House of Commons could resign to make way for Mr Burnham to run in a special election.Armed Forces Minister Al Carns has also been floated as a potential leadership contender, despite only having served in parliament since 2024.The former Royal Marine officer has made little secret of his ambitions, and his allies say while he won't initiate a challenge against the PM, he's ready to run should a contest be declared. Starmer vows to fight any challengeSir Keir, who won an overwhelming majority in the 2024 general election, is attempting to weather a string of ministerial resignations and scores of MPs' demands that he set out a timetable for his exit.A large majority of voters are frustrated with his government, which has failed to deliver on pledges to boost economic growth and improve living standards for working people, in part due to stubbornly high consumer price inflation.He has told allies that he will fight a leadership challenge should a rival stand against him, warning colleagues that any leadership contest would plunge the government into "chaos" at a time it should be focused on issues like the cost-of-living crisis and the war in the Middle East.Under Labour Party rules, any potential challenger to the prime minister would have to have the backing of 81 of the party's 403 MPs to make it onto the ballot.More than that number have publicly called on Sir Keir to quit in recent days.AP/ABC