Ed Miliband today admitted the race for Number 10 is 'neck and neck' as he launched Labour's election campaign at the Olympic park. The Labour leader used a speech at the top of the Orbit tower overlooking the London 2012 stadium to urge a 'spirit of optimism' and a belief that 'Britain can do better' He signalled once again that the NHS will be at the heart of his bid for power, announcing a new cap on the profits private firms can make from the health service. Scroll down for video . Labour leader Ed Miliband used a speech at the top of the Orbit tower overlooking the London 2012 stadium to urge a 'spirit of optimism' and a belief that 'Britain can do better' Mr Miliband laid out his pitch for power the morning after his mauling at the hands of Jeremy Paxman in the first TV contest of the campaign. Polls suggested David Cameron secured a narrow victory over his rival, but Labour strategists believe it exposed the Prime Minister's refusal to go head-to-head in a debate. Mr Miliband sought to counter claims his leadership has been too negative, vowing: Britain can do better than this'. He told activists gathered at the top of the 114metre sculpture at the heart of the Olympic Park: 'As we go out to fight this election, just remember: . 'They're the pessimists. We're the optimists. I know this election is going to be tough. 'Like so many races here during the Olympics, it may come down to the wire. Neck and neck. 'I know our opponents will throw everything they have our way.' But he insisted that Labour has 'a better plan, a better future'. Introducing Mr Miliband, deputy leader Harriet Harman said he had 'put us within touching distance of winning this general election'. Mr Miliband laid out his pitch for power the morning after his mauling at the hands of Jeremy Paxman in the first TV contest of the campaign . Mr Miliband announced a Labour government would act to ensure health services are no longer 'threatened' by privatisation . Mr Miliband announced a Labour government would act to ensure health services are no longer 'threatened' by privatisation. But he was forced to defend himself against claims that he was scaremongering by referring to 'privatisation' when no patients are expected to pay for their treatment up front. Under Labour's plans, a new profit cap - usually 5 per cent - would be set on outsourced healthcare contracts worth over £500,000, private companies would be blocked from 'cherry-picking' lucrative treatments and the NHS would become the 'preferred provider' for all services. Mr Miliband said of the profit cap: 'We do think it's right to say, when private sector companies are involved, we don't get excess profits which is draining money away from the National Health Service. 'Look, I think this is going to be common-sense thing that people will think is the right thing to do. I hope other parties adopt this because it's the right thing to do for the future of our NHS.' Mr Miliband set off on his campaign battlebus, urging supporters to be 'optimistic' for the future . Senior shadow minister Ed Balls, Ivan Lewis, Sadiq Khan, Rachel Reeves, Harriet Harman, Tristram Hunt, Yvette Cooper, Douglas Alexander and Chuka Umunna posed with Mr Miliband outside the bus . On people paying for private healthcare, he added: 'What is the real lesson of the past on this - the lesson before 1997 and a lesson I fear for the future if David Cameron were to get back in? 'It's that people end up having the option of either waiting for an unacceptably long time or having to go private - that that becomes the offer on the table for people. 'So I think there is a real fear that that becomes the option for people and you don't have a health service that is properly serving people so there's a big choice at this election and a big choice about the health service on the ballot paper.' Tory Health Secretary Jeremy Hunt said: ‘If you bankrupt the economy like Labour did last time – then you’ll put our NHS at risk. We can only have a strong NHS if we have a strong economy, but Ed Miliband doesn’t have an economic plan. ‘We all know Labour want to ‘weaponise’ the NHS but this is another policy from Ed Miliband that looks ill-thought through. It risks higher infection rates, higher waiting times and chaos for our NHS. This incompetence is exactly why Ed Miliband is simply not up to the job.’
Labour leader tries to recreate the 'spirit of optimism' of London 2012 . Puts the NHS at heart of his bid for power with new cap on profits . But he is forced to defence claims he is scaremongering on privatisation .