An extra 500 free schools will be opened by 2020 under a Conservative government, David Cameron announced today. The Prime Minister promised a major expansion of the policy which allows schools to be set up by community groups including parents, charities or teachers. But Education Secretary Nicky Morgan revealed she had blocked plans to allow profit-making in schools, which predecessor Michael Gove had advocated. David Cameron talks with school children during a visit to The Green School for girls in west London today . Free schools were introduced in 2010 to allow parents and community groups to set up their own schools. They are independent from local authorities but must still undergo Ofsted inspections. Supporters say they help to drive up standards by creating competition with existing schools, but Labour has opposed their creation in areas with a surplus of places where they are not needed. The new plan to open at least 500 of the schools by 2020 mean an extra 270,000 places. In a speech in London, Mr Cameron said: 'If you vote Conservative, you will see the continuation of the free schools programme at the rate you've seen in the last three years. 'That means, over the next parliament, we hope to open at least 500 new free schools resulting in 270,000 new school places. 'Remember - we're the only party that is committed to this. The only party that's opening up the education system so we can get more good places for your children. 'And isn't that what every parent wants - a great education for their child? You deserve the security of knowing your child is getting just that. And with the Conservatives you should expect nothing less.' He also backed the idea of existing grammar schools. Taking questions from the audience, Mr Cameron was asked about comments he made in 2007 that a 'pledge to build more grammar schools would be an electoral albatross'. He insisted: 'I have never said that grammar schools are an albatross, grammar schools are good schools and I like good schools. I want there to be good schools for people to send their children to. 'What I've said about grammar schools is, like other schools that are good, if they want to expand they should be able to expand. I have been very consistent about that.' The Prime Minister was joined by the Education Secretary Nicky Morgan (left) during a visit to The Green School for girls in west London . Mr Cameron said his party would pledge five hundred new free schools if the Conservatives win the general election in May . It comes as the government announces that 49 more schools have been given the go-ahead, taking the total created under the coalition to more than 400. Mrs Morgan, the Education Secretary, said: 'Free schools give pupils the chance to attend an excellent local school. 'They are providing more choice than ever before to parents and ensuring that children have access to a high-quality school place and the best possible education that prepares them for life in modern Britain.' Ms Morgan said she wanted each school to 'make the right choice for them' about whether to become a free school or academy. Asked if she could rule out a Tory government allowing free schools to make a profit, she told BBC Radio 4's Today programme: 'Yes I can rule it out, I think having for profit education is something that would make me feel very uncomfortable and it is not something that is needed. 'We have excellent sponsors like charities and others or parent groups wanting to run schools and they are doing an excellent job up and down the country.' Free schools were introduced in 2010 to allow parents and community groups to set up their own schools. They are independent from local authorities but must still undergo Ofsted inspections . Mrs Morgan's insistence that there would be no profit-making schools for the whole of the next parliament suggests a shift in policy from her predecessor. Mr Gove, who lost his job as Education Secretary in July, had advocated allowing profit-making to encourage companies to set up successful free schools. In May 2012 he said: 'It's my belief that we could move to that situation but at the moment it's important to recognise that the free schools movement is succeeding without that element and I think we should cross that bridge when we come to it.' Labour has criticised the free schools policy, claiming it can lead to money being channelled to areas where there is a surplus of school places instead of being targeted at areas where classes are overcrowded. Mr Cameron's plans for an expansion of free schools came as a report by the centre-right think tank Policy Exchange claimed they are raising standards for all pupils in areas where they open, even for children who do not attend them. The report suggested that the competitive effect created by a free school leads to improved academic standards in nearby under-performing schools. A Liberal Democrat spokesman said: 'This proposal simply masks the deep cuts the Tories are planning for education. Their scorched-earth policy for public services would mean that funding for nurseries, schools and colleges could be slashed by a quarter by 2020.' Chris Keates, general secretary of the NASUWT union, said: 'It is clear that if elected the Conservative Party will continue its obsessive ideological focus on structural change. 'It is scandalous that in the context where the Conservative Party is proposing even deeper cuts to funding post the General Election, it still plans to pour millions of pounds into free schools. 'There is no evidence that structural change raises educational standards.'
Cameron announces plans for 500 more free schools by the end of 2020 . Comes on top of more than 400 opened under the coalition government . Free schools can be opened by parents, charities and teaching groups . Prime Minister also backs expansion of existing grammar schools . Michael Gove supported the idea of schools making a profit when minister . But his successor Nicky Morgan says the idea makes her 'uncomfortable'