David Cameron has admitted Boris Johnson is aiming to be the next Tory leader . David Cameron has admitted Boris Johnson is locked in a behind-the-scenes battle with Theresa May and George Osborne to take over the Tory leadership. The Prime Minister said the London Mayor had 'suddenly realised' after years of mischief making that his main political rivals were those lining themselves up to take over the top job. He said Mr Johnson now understood the pair were no longer in 'competition'. The admission exposes the battle quietly raging behind the scenes over who will take over from Mr Cameron. It comes just weeks after Mr Cameron revealed he would stand down as Prime Minister before 2020 if he wins re-election next month. Mr Cameron said: 'Terms are like shredded wheat : two are wonderful but three might just be too many.' He named three of his senior colleagues - Home Secretary Theresa May, Chancellor George Osborne and London mayor Boris Johnson - as possible replacements as Conservative leader when he stands down. Speaking to his cousin Harry Mount in an interview with the Sunday Times, Mr Cameron also admits that his membership of the infamous Bullingdon Club at Oxford is 'cripplingly embarrassing'. Mr Cameron denied that he and the London Mayor have been political rivals for decades. But he admitted that Mr Johnson had, until recently, seen the PM as his competition. He said: 'He suddenly realised I'm not really his competition. His competition is people who'll have a crack at it after me.' Mr Cameron said he saw his relationship with the London Mayor as 'co-opetition'. He said: 'I wanted him to stand for London mayor. George and I helped persuade him to do that. And he's done it brilliantly. 'A Conservative is running the most successful city on earth, and is winning elections.' Mr Cameron said he remembered the London Mayor at Eton 'because he was so striking'. Boris Johnson has 'suddenly realised' that David Cameron is not his 'competition'. The Prime Minister said: 'His competition is people who'll have a crack at it after me' Chancellor George Osborne, pictured campaigning in Brentford this morning, and the Home Secretary Theresa May were named by the Prime Minister as potential successors . David Cameron's 11-year-old daughter regularly teases him for leaving her in the pub, his wife Samantha has revealed. Nancy jokes that she will write a memoir about her life as the daughter of a PM. Mrs Cameron said: 'She's always, like, 'I'm on Chapter Five of Daddy, How Your Life As Prime Minister's Affected Me. Chapter Two is when you left me in the pub'.' Mr and Mrs Cameron were left 'distraught' after leaving the then 8-year-old in the Plough Inn in Buckinghamshire after a Sunday drink in 2008. The Prime Minister, meanwhile, has told the Sunday Times that the family is kept together by his wife. He said: 'I love her as much today as when I first met her; more. Much more.' Mr Cameron added: 'It's easily the best thing that's happened in my life. I'm very blessed to have her. She is amazing.' He said: 'He was dishevelled. I remember watching him play rugby. He was ferocious. Built like a second row.' The Prime Minister also revealed that he had lost almost half a stone since Christmas after going on 'just a little bit' of a diet. Overall he lost 'two kilos'. Mr Cameron's admission that the London Mayor is lining up a tilt at the Tory leadership comes after Mr Johnson was accused of 'breath-taking cheek' after he set out his vision of 'moral purpose' in business and politics. The London Mayor praised the Coalition for having kept down unemployment and not returning to the dole queues of 1980s Britain. He said the fact that more jobs were being created was 'one of the absolute moral triumphs' of the government. The comments by Mr Johnson, who is standing to be a Tory MP in a west London constituency, were seen as an attempt to position himself as a future party leader. In 2004, Mr Johnson admitted a four-year affair with the journalist Petronella Wyatt while he was married to his second wife Marina, with whom he has four children. Five years later he fathered a child by Helen Macintyre, an unpaid adviser in the London Assembly. Mr Johnson spoke about morality in an interview with the London Evening Standard, saying he believed wealth creation was there to fund public services such as schools and hospitals. He said: 'I think this country was harrowed by the experience of mass unemployment in the early Eighties. 'One of the absolute moral triumphs of this Coalition government has been to get us through the worst recession for 50 years without seeing a return to those levels of unemployment.' But Labour's Stephen Pound, who is fighting to defend a nearby seat, said: 'I'm thinking of a sentence with the words pot, kettle and black in it.' 'It seems that Boris's motto is 'do as I say, not as I do'. It really is breath-taking cheek. He obviously has a different definition of 'moral' to most of my constituents.'
David Cameron revealed that the London Mayor had seen him as a rival . PM said Mr Johnson 'suddenly realised' his competition was elsewhere . Comes after he named Johnson, Osborne and May as potential successors . Mr Cameron also admitted Bullingdon Club past 'cripplingly embarrassing'