The 50% rule was first suggested last year by Ken Livingstone, the mayor of London. The news backs up a claim made by Livingstone that planning minister Lord Falconer had endorsed the plan. Typically, a local council will require that affordable housing make up 20-30% of a new development.
The government's plans are discussed in a report written by political consultant PPS for its private sector clients. It says that ministers will seek substantial increases in affordable housing for key workers and others.
"Ministers and officials have been impressed with the way in which Ken Livingstone has forced the issue, by stipulating that housing developments contain a 50% element of affordable housing."
Commercial office developments will also be required to increase the amount of affordable housing they are required to build.
A Whitehall source confirmed that some of the DTLR's proposals will be radical. He said: "There has been some thinking going on about this. They are revisiting the whole way affordable housing can be worked up."
Housebuilders will be concerned that Livingstone-style quotas will reduce the value of their developments.
Private housing consultant Roger Humber said that quotas of this kind would not solve the problem of the lack of affordable housing.
He said: "The problem will never be solved by salami-slicing the small amount of housing that is set to be built. There is a substantial undersupply of commercial housing for the market as well."
Gideon Amos, a director at the Town and Country Planning Association, said if such a strategy was adopted it would, in effect, be a tax on developers and was therefore unacceptable.
Amos admitted that the government would be aided by a recent High Court judgment that found that Oxford council had acted within its powers when it used supplementary guidance to increase the level of social housing in new developments. But he added: "To rely on the planning system to increase affordable housing is not sufficient."
Housebuilders have claimed that the use of supplementary guidance by Oxford council was an abuse of procedure.
The PPS report notes that developers could be asked to pay more money for planning permission.
It says: "Lord Falconer has accepted the argument that planning authorities are underfunded. As a result, the green paper will indicate that application fees should rise."
The green paper will also urge local councils to use their powers to assemble viable sites.
"The government has been exasperated at the failure of planning authorities to make use of the powers given to them to make compulsory purchase orders. They see it as a key barrier to their target of 60% of brownfield land being recycled."