Talking about planning from 2015 onwards, he said: “We need to start again, because we don’t have a system that’s fit for purpose.

“We need a fundamental reassessment of planning in England.

“How can we cease to be an embarrassment in the context of Western Europe on urbanism, on sustainable transport, on design?

“The system is highly deregulated and it seems to be probably in the poorest state since 1947 when it came into being.

Ellis went on to say that “the heart of darkness is the permitted development regime”, which allows commercial premises to be converted into homes without needing planning permission.

The PD rights “unlock two fundamental tenets” of the 1947 Town and Country Planning Act, he said: the nationalisation of development rights and democratic comprehensive planning.

The development outcomes of the PD rights, he said, “are going to be very poor”, adding: “Are we committing ourselves to the slums of the future?

“Is this really what the fifth-richest country on earth wants to leave as a legacy?”

Speaking earlier, chief planner Steve Quartermain, reading a speech from planning minister Brandon Lewis, said the office-to-residential permitted development rights had “proved to be successful” and were helping to deliver new homes on brownfield land.

Calling for more ambition, Ellis said a new purpose for planning was needed so that it is “outcome-led” rather than “process-led”, with its social purpose restored.

His wishlist for the next government included a national plan and the reintroduction of the New Towns Act with 10 areas designated for new settlements. Ellis also called for and an update to the National Planning Policy Framework (NPPF) and better building standards.

Elsewhere, Chris Tinker, regeneration chairman of housebuilder Crest Nicolson, said developers faced problems dealing with neighbourhood planning and had little representation in the process.

“So you have a system of land allocation being done without the deliverer,” he said.

Tinker also said it was beyond the resources of housebuilders like Crest to deliver a garden city or large urban extension, something that would require the government to lead on.

Local and neighbourhood planning would never deliver the major housing sites of 10-15,000 homes, he added.

Other speakers, including Alice Lester, programme manager at the Planning Advisory Service (PAS), expressed support for a national spatial plan.

But shadow communities secretary Hillary Benn, speaking later, confirmed that the Labour Party had no plans to introduce such a plan if it came to power in next year’s general election.

Labour would “leave in place” the NPPF, said Benn, though it would strengthen its requirement to build homes on previously-used brownfield land.

Under a Labour government, “every community must take responsibility for meeting its own housing need”, said Benn, and would be given tools to make sure schemes granted planning condition are actually built out by developers.