Michael Gove's department was accused of lying tonight in a furious turf war that left the Education Secretary sidelined when David Cameron appeared to side with the Deputy Prime Minister.
Nick Clegg has announced an extra £150 million for schools to help them get their kitchens and dining rooms up to scratch so they can meet his plan to offer every five to seven-year-old a free school dinner.
But while he made a visit to a school in Lambeth as he prepared to confirm the cash, sources linked to the Department for Education are understood to have briefed reporters that the DPM was possibly planning to raid the basic needs budget, used to meet the demand for extra places, to fund the move and then later dismissed claims that unspent cash was available in the maintenance budget to cover the cost.
In a particularly robust counter-briefing senior Liberal Democrat sources accused the DfE of lying, going rogue, being hostile and "talking bollocks".
Downing Street then made clear that it was Tory Mr Gove's department that were out of line.
"The position is absolutely the one the DPM's office have set out," the Prime Minister's official spokesman said.
Relations between Mr Clegg and Mr Gove have appeared strained for many months, with the Liberal Democrat leader criticising the use of unqualified teachers and blocking plans to allow nurseries and childminders in England to look after more children.
Today's announcement of new funding to allow schools to build kitchens and expand dining rooms will be included in tomorrow's Autumn Statement. The Treasury will be stumping up £70 million and the remaining £80m will come from underspend in the school maintenance budget. The money is on top of £450m set aside in 2014/15 and £635m in 2015/16 to fund the free lunches plan, which is expected to save parents around £437 per year, per child.
A senior Liberal Democrat source said: "This is a decision taken jointly as a Coalition government at the very highest level of the Coalition government at the Quad (Prime Minister, the Deputy Prime Minister, the Chancellor and the Chief Secretary to the Treasury).
"It was something that the Chancellor and Prime Minister entirely signed up to and that's why we have agreed the funding as we have.
"I think what you have seen from DfE is them going rogue and a slight bitterness at the fact that this policy wasn't invented there but they are completely out of step with the rest of government whether they are coloured yellow or blue and they need to come in line with the rest of the Government."
He added: "It's time for them to stop whining and get behind a policy that they are going to have to deliver because all of the rest of government is agreed with it."
Told that departmental sources were insistent that the £80 million did not exist, he replied: "The DfE are talking bollocks. The Treasury and the DfE know, and David Laws is the one that has worked all this through, there is a £157 million maintenance underspend of which we are going to spend £80 million on this and they are going to spend the other money on free schools.
"That is a fact. The DfE are lying to you if they are saying otherwise."
"When decisions are taken by the Prime Minister, the Deputy Prime Minister, the Chancellor and the Chief Secretary to the Treasury departments, even if they don't like it and even if they would have preferred to spend the money on something else, to go out and try and trash the policy is not how it works. That's not cricket.
"I get the sense that they are hostile to ideas that are not their own."
"The DPM wants the DfE now to row back and get with the rest of the government in backing a popular, innovative and exciting policy."
Anne Bull, chair of caterers organisation LACA said: "This is a welcome announcement that recognises the extra costs some schools will have to provide the necessary kitchen and serving facilities. Catering staff will be working closely with their headteacher and leadership teams in their schools to ensure that that this new government money is used wisely and reaches those schools that need it."
Mr Clegg said the Government was "making the sums add up" to fund the schools meal plan by finding money from a number of sources.
During a visit to Walnut Tree Walk Primary School in Lambeth, where he sat with pupils to eat a school lunch of chicken and rice followed by crumble with custard, he said: "The Chancellor will set out the details tomorrow but we are making the sums add up by closing the loopholes in our tax system, we are making extra efficiency savings in Whitehall, we are putting new money, for instance, forward to help schools expand their kitchens or buy new equipment, and part of that money also comes from maintenance funds that the Department for Education haven't managed to spend elsewhere."
He added: "For a long time I've been wanting to deliver free healthy lunches to all children in infant school because, not only does it save money for the families having to pay for those lunches at the moment - actually doing that every year costs a family about £400 - it's also, all the evidence says, a great, great way of actually helping children concentrate in the afternoon after the lunchtime.
"It bring children together from different backgrounds so it helps close the attainment gap so it's good for education, it's good for giving children, particularly from poorer backgrounds, a real boost and it's good, of course, to save money for families as well."
The Lib Dems have estimated that 1.5 million more children will receive free school meals when the scheme takes effect in September next year, on top of the 400,000 who are already entitled to them.
The initiative will also end an anomaly that meant poor teenagers attending a further education college were not eligible for free dinners, while those at a school sixth form were.
Proposals for free school lunches were first mooted in an independent review of school food, published in the summer.
The review, by Henry Dimbleby and John Vincent, co-founders of the Leon restaurant chain, called for free meals to be extended to all primary schools, starting in the most deprived areas of England.
Mr Vincent said: "We spent a year analysing food in schools from every angle. Free school meals for all children, in this case in infants classes, benefits all children and especially the poorest children. Children will do better at school, be healthier, and the tax payer will spend less on fixing diabetes and other diseases caused by bad diet."
Russell Hobby, general secretary of the National Association of Head Teachers (NAHT), said: "It's funding for the equipment which is the biggest concern. Far fewer schools have kitchens than anybody thought.
"Free school meals are a good idea, but we need money to build the facilities that will be needed to provide them."
He added: "Building the facilities to deliver this policy is essential. There's going to be a lot more children eating meals and we don't want to have long lunchtimes with children eating in shifts.
"This sum of money seems like it will go some way to delivering the policy. It will be challenging to get it done in the time period, but it's a good contribution."
Chief Medical Officer Professor Dame Sally Davies said: "I welcome this initiative. We know healthy school meals improve both the health and educational attainment of our children, which can only be seen as a good thing."
Shadow education minister Lucy Powell said: " David Cameron and Nick Clegg scrapped Labour's plans to extend free meals for school children on taking office. Now they talk about helping with school meals, but in reality this Tory-led Government will have taken up to £7 billion a year of support away from children by 2015.
"Families facing a cost-of-living crisis deserve better than this. Labour would extend free childcare provision for three and four-year-olds with working parents from 15 to 25 hours a week and give parents a guarantee of wrap-around care for all primary school children."