Special report: Coalition in crisis over free schools and academies

Lib Dem leader attacks Conservative policy on educational institutions that don't have to meet core standards

Free schools and academies must employ qualified teachers, Nick Clegg will demand this week, in the first break with the Conservatives on education policy under the coalition government.

The Deputy Prime Minister will deliver a hard-hitting speech that will put pressure on the Conservatives over the lack of appropriately qualified teachers in free schools, including the crisis-hit Al-Madinah school in Derby.

Mr Clegg will pledge a new "parental guarantee" in the Liberal Democrat election manifesto, reassuring parents that their child's teacher will be qualified if the party is in government after 2015. Under the guarantee, free schools and academies would also have to stick to the national curriculum and follow nutritional standards for school meals. The policy puts the Lib Dems at loggerheads with David Cameron and Michael Gove and aligns them more closely with Labour on education.

In a clear dig at Mr Gove, the Education Secretary, Mr Clegg will declare: "Parents don't want ideology to get in the way of their children's education."

His challenge comes as a poll for The Independent on Sunday reveals today that just over a quarter of people believe that parents, teachers and charities should be encouraged to set up new free schools even if there are already schools in the local area. The ComRes poll found that 36 per cent are against, while 37 per cent don't know.

The coalition split over one of the most contentious areas of schools policy emerged as research shows a dramatic rise in the number of unqualified teachers in free schools and academies, rising by 141 per cent in three years. Labour figures showed that one teacher in every 10 in free schools does not have a teaching qualification, or nearly 5,300 individuals across all non-maintained schools. At the same time, there are 6,000 vacancies for teachers in all state-funded schools, suggesting an impending crisis in the profession.

Under current policy implemented by Mr Gove, all schools free from local authority control, including the controversial free schools, can employ staff without teaching qualifications, do not have to adhere to the national curriculum and do not have to follow nutritional standards. This last "freedom" has enraged chef and nutrition campaigner Jamie Oliver, who says the concept of a healthy meal is being eroded in academies and free schools. But it is the area of teaching qualifications that is the most controversial. In the past few weeks, there have been high-profile cases in which teaching staff, including headteachers, of free schools have been forced to step down after criticisms by Ofsted that they were unqualified or underskilled.

The Al-Madinah Free School in Derby is currently closed after being classed by inspectors as inadequate and the headteacher underqualified. Pimlico Primary Academy lost its 27-year-old headteacher, who also had no formal qualifications in the profession, earlier this month. The headteacher of a third school, the Discovery New School, a Montessori primary in Crawley, West Sussex, has stood down in the past few days. Ofsted classed this school as inadequate for having staff without the right skills and leadership for the education of children. Earlier this year, Ofsted said that Lindsey Snowdon, the head of the Discovery school, "lacks the skills and knowledge to improve teaching". Mrs Snowdon resigned last week.

In a speech on Thursday, Mr Clegg will unveil a Liberal Democrat manifesto promise that all free schools and academies must adhere to the national curriculum and employ staff with qualified teacher status, or be working towards a qualification, such as under the fast-track Teach First programme.

Lib Dem sources said ministers had raised the "parental guarantee" policy with their Tory counterparts, with the suggestion that it could be implemented this parliament, but recognised this was something that was "never going to happen" under a Conservative-led government.

Instead, the Lib Dems will make it one of the key pledges of their manifesto for the 2015 general election. The parental guarantee will also ensure that every child has a school meal of high nutritional standards.

The Lib Dems insist that they still strongly support the idea that headteachers of academies and free schools should have increased autonomy, but also that basic standards should not be tossed aside.

The Deputy Prime Minister is expected to say: "We believe greater autonomy enables school leaders to take responsibility in those areas where they know what's best for their pupils, while also giving them the freedom to innovate. But it shouldn't surprise you if I say that, although we work well with the Conservatives, our two parties still have differences of opinion, some strongly held. Looking to the future, there are aspects of schools policy currently affected by the priorities of the Conservative Party which I would not want to see continue.

"For example, while I want to give schools the space to innovate, I also believe every parent needs reassurance that the school their child attends, whatever its title or structure, meets certain core standards of teaching and care – a parental guarantee, if you like.

"Parents don't want ideology to get in the way of their children's education. They don't care about the latest political label attached to their child's school. What they want, and expect, is that their children are taught by good teachers, get taught a core body of knowledge, and get a healthy meal every day. What's the point of having a national curriculum if only a few schools have to teach it? Let's teach it in all our schools. And what's the point of having brilliant new food standards if only a few schools have to stick to the rules? Let's have quality food in all our schools.

"Diversity among schools, yes. But good universal standards all parents can rely on, too. And, frankly, it makes no sense to me to have qualified teacher status if only a few schools have to employ qualified teachers."

The Al-Madinah Free School was found by Ofsted this month to be "dysfunctional" and inadequate in all areas; "most of the primary school teachers have not taught before" while large numbers of "unqualified staff desperately need better support and training".

Of the 28 state primaries surrounding the Discovery school, 25 had surplus places – underlining fears that some free schools are being set up where there is no demand. Some 16 of those 28 were rated "good" or "outstanding" by Ofsted. The Government's own impact assessment of the Discovery school in 2011 claimed that the competition it would provide would encourage surrounding primaries to "raise their performance in order to retain pupils in order to remain financially viable".

Labour has also pledged that teachers in all state-funded schools will have to be qualified or working towards a teaching qualification.

Labour's education spokesman, Tristram Hunt, said: "We only have to look at the mess at Al-Madinah Free School to see how dangerous it is that David Cameron and Michael Gove are allowing unqualified teachers to be permanently employed in our schools. Oftsed found that school to be inadequate on every single measure and too many unqualified teachers were at the heart of its failure."