Housebuilders have urged the government to toughen up its PPS3 draft guidance to prevent local authorities dictating the mix of schemes.

At a Home Builders Federation seminar in Birmingham last week developers told ODPM and Treasury officials that PPS3 gave councils too much leeway to determine the mix of schemes.

Officials say that the composition of large developments ought to mirror the demand for dwelling types. This is to be determined by the housing market assessments that PPS3 will oblige authorities to draw up.

Consultant Roger Humber, who also met ODPM officials to discuss PPS3 last week, said: "There is still a great deal of concern. Why on earth are local authorities being required to make all this effort to draw up the housing market assessments if it is not to prescribe."

The government had proposed to allow councils more power to stipulate the make-up of schemes. It dropped that idea after an industry backlash last year.

Deputy prime minister John Prescott has told the Barnet council to reduce the minimum size of schemes that must include affordable housing from 15 to 10 dwellings. Barnet's proposals, which are in its development plan, are in line with the minimum benchmark in PPS3.