Homeowners will be able to build kitchen extensions, loft conversions and conservatories without planning permission under sweeping changes to speed up housing developments, The Times has learnt.

The proposals, to be announced by Ruth Kelly, the Communities Secretary, on Monday, are part of the biggest shake-up of planning laws for 20 years. They will be welcomed by thousands of would-be home improvers who cannot afford to move due to stamp-duty rises.

But neighbours may find it much more difficult to stop extensions or conversions next door which could overlook their gardens or shut out some of their sunshine.

At present homeowners have to pay up to £1,000, including drawings, to obtain planning permission for minor alterations which can take between eight and sixteen weeks. Permission is needed for solar panels, satellite dishes, wind turbines, loft conversions, porches and extensions to the back or sides of properties.

Planning authorities process 350,000 domestic applications a year, of which more than 90 per cent are granted immediately because there is no damaging impact on a neighbour’s property.

Under the new proposals, to be published in a consultation paper, most home improvement developments will be able to go ahead immediately provided that they comply with height and depth restrictions and meet an “impact test”. As a result councils will be able to focus their resources on more complex applications for the building of new homes.

Those owning detached homes will be able to extend the width of their properties by 50 per cent without planning permission. They will be able to build out at the back by four metres and up to the height of the roof. They will also have much more flexibility to build garages and bike sheds in their gardens.

The planning White Paper will also allow councils to fast-track small domestic and commercial extensions, unless they are proposing a change of use. These account for a further 300,000 small applications.

In addition the paper will propose a new independent commission which will take decision-making on all major planning developments away from local communities. This will cover nuclear power stations, road and rail projects, airports and all big housing developments.

The paper is also expected to make controversial proposals to allow more supermarkets on the edge of towns and change green-belt boundaries to allow more building on the urban fringe. All the proposals, backed by Gordon Brown, are designed to cut through bureaucracy and speed up economic development.

Ministers are concerned about the relentless rise in household planning applications, up 11 per cent since 1995, as homeowners improve rather than move, which is clogging up the planning system.

The changes to household planning alone are expected to reduce the number of domestic applications that have to be processed by 90,000 – 25 per cent of the total workload.

A Whitehall source said: “The local planning system should support people’s aspirations to improve their homes rather than act as a barrier. Many people do not want to move but do want more room.” Planning experts last night welcomed moves to cut through red tape but gave warning that impact assessments could cause difficulties. Gideon Amos, chief executive of the Town and Country Planning Association, said: “Freeing up household applications must be used to speed up other major and more complex developments, not create problems.”

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