Sweeping reforms to the planning system could lead to social housing facing “extinction”, critics have warned.

Housing secretary Robert Jenrick said the biggest overhaul of planning policy in England in decades would protect green spaces while making it easier to build on brownfield sites.

The government’s over-arching aim to curb the power of local politicians was clear as Jenrick said it takes seven years to agree housing plans and five years just to get a spade in the ground – and the proposed changes aim to speed up the process.

But campaigners were alarmed by the consequences of the slashing of red tape, seizing in particular on the government proposing to scrap Section 106 agreements, which can be used to require private developers to build a certain amount of social homes on a site.

While an obscurity to most outside the building world, Section 106 is said to be responsible for half of all affordable homes built in England. It will be replaced by a new “infrastructure levy”. Without it, Labour branded the shake up a “developers’ charter”.

Despite the government’s insistence that the moves would create tree-lined streets and promote “beautiful” buildings, the Royal Institute of British Architects (RIBA) said there was “every chance they could also lead to the creation of the next generation of slum housing”.

Kate Henderson, chief executive of the National Housing Federation, said: “Any alternative to Section 106 must ensure we can deliver more high quality affordable homes to meet the huge demand across the country.”

Polly Neate, chief executive of housing charity Shelter, said: “Decades of political decisions have left social housing gravely endangered.

“If the government now removes the requirement for developers to build their fair share it could face extinction.

“Over a million households on waiting lists for social homes risk having their hopes dashed.”

Prime minister Boris Johnson and his senior aide Dominic Cummings have both advocated reform to the system and the proposals in the Planning for the Future White Paper published on Thursday set out the government’s vision.

Part of the new process will involve quicker development on land which has been designated “for renewal”, with a “permission in principle” approach that the Ministry of Housing, Communities and Local Government (MHCLG) said will balance the need for proper checks with a speedier way of working.

The other two categories will see land designated for growth where new homes, hospitals and schools will be allowed automatically to empower development, while areas of outstanding natural beauty and the green belt will come under the protection category.

Jenrick added: “These once-in-a-generation reforms will lay the foundations for a brighter future, providing more homes for young people and creating better quality neighbourhoods and homes across the country.

“We will cut red tape, but not standards, placing a higher regard on quality, design and the environment than ever before.”

It also aims to boost the share of houses built by small and medium-sized building firms, which built 40% of new homes 30 years ago but only 12% today.

The White Paper proposes that all new streets should be tree-lined and the MHCLG also says “all new homes to be carbon neutral by 2050, with no new homes delivered under the new system needed to be retrofitted”.

Councils will also be forced to lay out a “local plan” of where new homes can be built, as only 50% have such schemes in place.

The reforms aim to reduce the number of planning cases that get overturned at appeal by creating a “clearer, rules-based system”.

A new national levy would replace the current system of developer contributions and “beautiful buildings” will be fast-tracked through the planning system.

But RIBA president, Alan Jones, said: “While there’s no doubt the planning system needs reform, these shameful proposals do almost nothing to guarantee the delivery of affordable, well-designed and sustainable homes.

“While they might help to ‘get Britain building’ – paired with the extension of permitted development – there’s every chance they could also lead to the creation of the next generation of slum housing.”

Shadow housing minister Mike Amesbury said: “This is a developer’s charter that will see communities sidelined in decisions and denied vital funding for building schools, clinics and community infrastructure.”

An MHCLG spokesperson said: “These claims are completely untrue.

“Our proposals will introduce a simpler levy that ensures developers deliver at least as much – if not more – affordable housing.

 “We are prioritising high quality design for all new homes. For the first time every local area will develop their own mandatory design codes – these will decide the development which can happen in their area, with new building only allowed if they reflect local character and preference.

“Developments will only be fast-tracked if they are high quality and meet locally-designed codes and any new buildings would be subject to our stringent regulations.”