Nick Clegg has accused the Tories of failing to enforce "basic standards" in schools as he dramatically disowned key planks of the coalition's education policy.
The Deputy Prime Minister opened coalition dividing lines by insisting all teachers should be qualified, and the national curriculum should be taught in every school.
Speaking on Sky News' Murnaghan programme, Mr Clegg insisted his criticism of "ideological" measures championed by Conservative Education Secretary Michael Gove was not a government "crisis" or political positioning, but a "perfectly sincere difference of opinion".
"This is something I have made clear publicly and privately in government for a long time," the Liberal Democrat leader said.
"Coalition works that we agree on a lot on education... but of course there are tensions and pinch points. We are not identical parties."
Mr Clegg said: "The Conservatives really don't want any minimum amount of basic standards to apply to schools who have these new freedoms. And I think what we need to do is a sensible balance."
He insisted it was "complete and utter nonsense" to suggest the Lib Dems were adjusting their policy to appeal to Labour in the case of another hung parliament in 2015. The Opposition wanted to "strangle" school freedoms, he said.
Mr Clegg also played down suggestions of a rift with fellow Lib Dem and schools minister David Laws, who last week defended the performance of unqualified teachers.
"David Laws is right that that is the policy of the Department for Education. He is quite right in stating that is the present approach," he added.
Mr Clegg will detail his party's approach in a speech at a London school on Thursday.
"I'm proud of our work over the last three years to increase school autonomy, which, in Government with the Conservatives, has been through the academies programme," he is expected to say.
"And it is Lib Dem policy to give all schools, whether they are academies or not, those same freedoms to attract and reward excellent teaching, set their own term dates and vary their school day.
"We believe greater autonomy enables school leaders to take responsibility in those areas where they know what's best for their pupils, whilst 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, whilst 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."
Mr Clegg will ask: "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.
"That's my philosophy. Diversity amongst 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."
Mr Clegg will say that over the last decade there has been a "revolution in the way in which we've recruited and trained our teachers", including schemes such as Teach First and Schools Direct.
"What all of these routes have in common is that at the end of them you're recognised as a qualified teacher," he will add.
"And I want every parent to know that their child will benefit from this kind of high quality teaching.
"That's why I believe we should have qualified teachers in all our schools."
A DfE spokesman said: " Free schools are raising standards and giving parents more choice.
"They are run by teachers - not local bureaucrats or Westminster politicians - and are free to set their own curriculum, decide how they spend their money and employ who they think are the best people for the job. This Government is not going to take these freedoms away.
"Independent schools have always been able to hire brilliant people who have not got qualified teacher status (QTS).
"Free schools and academies now have the same freedoms as independent schools to hire great linguists, computer scientists, engineers and other specialists so they can inspire their pupils."
Tory education minister Liz Truss told ITV News she remained fully behind free schools.
"I think it is important that they have freedom over teaching and over the curriculum. I think that is what is making them successful," she said.
"I am slightly surprised to hear what Nick Clegg has to say. Because on Thursday David Laws made an impassioned speech in favour of free schools having these freedoms.
"So there seems to be a bit of confusions about their policy but we are very clear that the government policy is that free schools should have that freedom.
"The proposals went through on free schools with Liberal Democrat support. This is a new thing that we have heard and I think it is partly to placate parts of the Lib Dem party who may not be happy with the policy."