Theresa May has savaged Boris Johnson and Dominic Cummings’ housebuilding reforms, warning they make a mockery of their claim to be “levelling up” the north and south of England.

In a Commons debate, the former prime minister ridiculed her successor’s proposals to replace local planning controls with an algorithm that will “distribute” an annual 337,000 homes across the country.

The scheme, reportedly the brainchild of the PM’s chief advisor Cummings, could deliver an additional five million homes across England in the next 15 years, with nearly a third in rural counties.

May was joined by 31 Tory MPs, including six of her former cabinet ministers such as Jeremy Hunt and Damian Green, as they unanimously passed a motion demanding that the project be paused until after parliament has voted on it.

The PM has been bullish in recent days as the Tory rebellion has grown, but backbencher Bob Seely warned him that the government reforms represented “not levelling up but concreting out” many areas.

The Sunday Times reported this summer that Cummings had been working with communities secretary Robert Jenrick devise the radical planning changes, which are based on US-style zonal developments.

A petition opposing the move has already attracted nearly 150,000 signatures.

One Tory MP told HuffPost UK: “This is government by spad [special advisor] and proves that people like Dominic Cummings have no idea how to implement policy.

“This could have a longer impact on the government than Covid. If they go ahead, it won’t be us they have to deal with, it will be the electorate in the local elections next year and the year after that and after that.”

The criticism came as Cummings. who has set up a new Nasa-style ‘command centre’ to better coordinate No.10′s oversight of Whitehall, is facing fresh scrutiny from parliament over his role.

The Commons public administration and constitutional affairs committee on Thursday launched a new inquiry into “the role and status of the prime minister’s office”.

May, who has already criticised Johnson over his plan to break international law on Brexit, was withering in her criticism of the “ill-conceived” reforms.

She said: “The problem with these proposals, the problem with this algorithm on housing numbers, is that it doesn’t guarantee a single extra home being built and, far from levelling up, it forces more investment into London and the south.”

In a pointed reference to this year’s A-level fiasco, the former premier said: “I would have thought that the Government might have abandoned algorithms by now.”

“What this new algorithm does, as regards to levelling up, is flies in the face of the government’s flagship policy. The government needs to think again and come back with a comprehensive proposal to this House for a proper debate and, dare I say it, a meaningful vote,” she said.

Seely earlier warned the reforms could “hollow out our cities” and “urbanise our suburbs”.

“I support levelling up 100% but, broadly speaking, the danger in these new targets in the way they’ve been shaped is that the biggest housing increases will be to rural shires and suburbs, and the biggest falls are in the urban north and Midlands.

“The worst of all worlds would be to hollow out our cities, to urbanise our suburbs and suburbanise the countryside and yet I fear that is what we may accidentally be achieving. That is not levelling up but is concreting out.”

Hunt said: “The argument for building new houses has been won but what is on the table risks eroding local democracy, reducing affordable housing and encroaching on our beautiful countryside.”

May’s former deputy Damian Green added: “We are in danger of turning the Garden of England into a patio.”

Conservative former cabinet minister Chris Grayling told the government he could not support the housing algorithm, claiming the approach is “wrong”.

“The reality is if we go ahead with a housing approach of the kind the government is setting out in this algorithm, what it will do is it will continue to suck economic growth, the brightest and best people in our society and opportunity into the south-east of England – exactly the opposite to what this country actually needs to achieve,” he said.

Consultation on the government’s White Paper on the reforms is due to end this month and MPs think legislation is likely in the new year.

Housing minister Chris Pincher assured MPs that their concerns would be reflected on “very carefully”.

“I am especially mindful that honourable members are concerned about geographic imbalance – concerns about too many homes in the south and not enough in the Midlands and the north,” he said.

“Equally, I recognise anxieties about what these changes might mean for our countryside in contrast to our urban areas.”

“I want to reassure the House that through this consultation process we are committed to addressing any supposed imbalances.”

The prime minister’s official spokesperson said he had not heard May’s remarks but said: “Unnecessary delays to the planning system are stopping us from building a better Britain.

“We must reform the planning system to cut red tape and make the system faster while ensuring councils and local people can decide where developments should and shouldn’t go.”