Dominic Cummings writes on his blog: 'I want people in No 10 to realise every time they interfere in the Department for Education with some stupid gimmick, the story might go badly wrong'

The former special adviser to the education secretary, Michael Gove, has warned No 10 there will be further leaks if the Liberal Democrats try to impose any more "stupid gimmicks" on Gove's schools revolution.

Dominic Cummings also claimed his former boss regarded as a joke a joint article he been ordered to write with the Liberal Democrat schools minister David Laws claiming the two wings of the coalition were united behind Nick Clegg's plan for universal free school meals this autumn.

He gave an insider's account of how Clegg had ordered Cameron and then Gove to write the article in the Times in a bid to reassure teachers that the policy was going ahead.

Cummings, described as the brains behind Gove's schools revolution, wrote on his blog: "I blew this up because I want people in No 10 to realise that every time between now and next May that they interfere in the Department for Education with some stupid gimmick, the story might go badly wrong because someone will leak something. I want Cameron to grit his teeth and say, 'Cleggy, I know you need your gimmicks, and you can have them, but why don't you go and play somewhere else, if you go near the DfE again, it will probably just go tits up.'"

Cummings told Clegg: "You have a vague hope this nightmare can be turned around, but you don't know how to do it. It can't. Because your organisation, strategy and message are hopeless and you don't even have clarity about your own goal."

He said No 10 should lock Clegg up, but instead "they send him out this morning like a balloon that they've let go of, to whizz around the broadcast studios making himself even more of a laughing stock".

Cummings added that Clegg had blown his own credibility by conceding in interviews that he had demanded Gove pen the joint article, an admission that damaged the credibility of Gove's avowed support for the policy.

Cummings wrote: "You cannot turn the story around now. Nobody with an IQ >75 is going to believe you when the leaked emails show I was telling the truth."

The extent to which Cummings now operates as a free agent or with the approval of Gove has always been unclear. Cummings no longer works for Gove or the government, departing at the end of January, and is now unbridled in his criticism of Clegg's methods.

But Liberal Democrats are furious with Cumming's continued guerrilla war against Clegg claiming he is breaching the civil service code, which states "special advisers must continue to observe their duties of confidentiality after they have left their employment as a special adviser have a duty to maintain confidentiality".

Conservative sources said efforts had been made to rein in the former special adviser, but no obvious sanction was available.

In broadcast interviews on Thursday, Clegg described Cummings as "a rather peculiar former Conservative adviser" who has allowed his former role to go to his head. He said Cummings was unerringly wrong.

But Cummings claims there was a lack of planning, funding and preparation of the proposal, which was made last September at the Liberal Democrat conference. He denounced the plan as a gimmick typical of Whitehall and said it had been drawn up "on the back of a fag packet".

He has also called for Clegg to lose his chairmanship of the cabinet home affairs committee, claiming he was misusing the position to promote his own personal position.

Some of the criticisms have been echoed by headteachers who claim they have not been given sufficient funds or time to extend their Kitchens to meet higher demand. There is also a dispute over whether Clegg has raided other education department budgets to fund the capital programme.

Exasperated by the row leading to further leaks of Whitehall correspondence last week over knife crime, Clegg this week demanded Cameron rein in Gove, prompting the joint article in the Times. In a string of broadcast interviews Clegg said the free school meals policy would go ahead. "It's going to happen, it's properly budgeted, it will happen," he said.

"If you really want to know about all this argy-bargy in Whitehall – which I don't think is of much interest to the parents and the teachers, and the children who are actually going to benefit in September – but there's a few rather peculiar Conservatives and former Conservative advisers who don't like this policy and seem to be spending a lot of time trying to discredit it. I think it's a pity, because frankly their views are irrelevant.

"You have this from time to time in politics, you have people who aren't elected to anything, don't have any authority of their own, and when they get a backroom adviser's job it all slightly goes to their head," he told ITV's Good Morning Britain.

He said Cummings was "flatly wrong" on every detail of the announcement.

Clegg pointed to the Times article saying Gove and Laws "have come out publicly just to quell any noises off and say: 'Look this is going to happen, it is properly funded.'

"And I'll tell you what, it's going to be a really, really important boost to families up and down the country who are paying £400 a year to pay for school lunches. It's been shown – because we've tested this over many years – to have a dramatic effect on kids' ability to concentrate in class in the afternoon, it's got a very good effect as well of having children mix together at lunchtime."

Clegg insisted the plan had been piloted in Durham and Newham, and the nationwide scheme was not being introduced any faster than in the pilot regions. He said the government had set aside money on top of the £1.4bn to maintain schools generally.

"We think the resources are there. The detail is now in the discussion between the individual schools and the local authorities."