Andy Burnham is risking a fight with Labour MPs on tightening benefits rules as he warned Britain 'must get really serious' about curbing welfare.The Prime Minister suggested his plans for reform could make payments more 'conditional upon people taking opportunities that are presented in front of them'.But he pushed back against pursuing a 'crude approach' to bringing down spending, as he warned about 'crude cuts to benefits to get the welfare bill down'.The number of people in England and Wales claiming Personal Independence Payment (PIP), the main disability benefit, has passed four million for the first time. The number of claimants has roughly doubled since 2019, with spending on PIP forecast to rise to more than £41billion by the end of the decade.PIP is intended to help with everyday tasks and extra living costs if someone has a long-term physical or mental health condition or disability. It has been revealed that teenagers claiming PIP for conditions such as anxiety receive £100 a week more than part-time workers on a minimum wage.Keir Starmer's efforts to tighten rules for claiming PIP were derailed last year by a huge rebellion from his own Labour backbenchers. But Mr Burnham, now that he has ousted Sir Keir from Downing Street, suggested he is ready to make a renewed case for benefits reform to his party.He is also expected to this week make an intervention on the one million young people not in education, employment or training - so-called NEETs. Andy Burnham has signalled he is ready to face down Labour MPs on tightening benefits rules as he warned Britain 'must get really serious' about curbing welfare Data from the Department for Work and Pensions (DWP) showed there were 4million claimants entitled to Personal Independence Payment (PIP) at the end of April'I think we've got to get really serious as a country at getting the welfare bill down,' the PM said in an interview with the BBC's Laura Kuenssberg.Asked if there were people claiming benefits who don't need them, Mr Burnham replied: 'I wouldn't necessarily go straight to blaming those people.'What I would say is that there are people in the benefit system, young people in their 20s, who have been, I would say, quite seriously let down because the support wasn't there for them when it should have been there.'So I'm talking about a school system that doesn't have the right support for young people with special educational needs or disabilities.'I'm talking about an education system that for a very long time has been obsessed on the university route but hasn't done enough... for young people who want technical qualifications and in many ways has treated them as second class students, hasn't done enough for young people at 16 who want to get an apprenticeship, a work-related opportunity.'Pressed on how he might attempt to cut the ballooning welfare bill, the PM added: 'It's about changing the nature of the support and making some of the support conditional upon people taking opportunities that are presented in front of them.'I think it's a good thing that the Government has given guarantees of opportunities for young people, and I think we need to continue down that approach, and where mental health support is needed, for instance, it's provided in work to support people in an opportunity.'Mr Burnham also claimed that his promise of a council house building boom would, over time, help cut the welfare bill as it would reduce spending on housing benefits.He added: 'I'm just pushing back on is this idea that we go to a kind of crude approach, crude cuts to benefits to get the welfare bill down.'Often that just pushes people into even more crisis and then even more public spending in another part of the system. We need a system that sets people up for success rather than pays for failure.'