The financial viability of a landmark £404m regeneration project in London is being hampered by rising build costs and new social housing rent laws.
The cost of a proposed redevelopment of the Aylesbury Estate in Southwark, London – the first to win funding under the government's New Deal for Communities programme – has risen from £289m to £404m.

This is because a consortium led by Mace has increased the density of the proposed residential redevelopment on the 24 ha estate to fund more community facilities.

In the latest proposals unveiled on Tuesday, 2000 houses will be demolished, 674 homes will be refurbished for rent, 1000 built for rent and 900 built for sale, including a 31-storey steel and glass tower.

Tenants are to vote on the proposals in the autumn. A yes vote would mean the transfer of 2518 dwellings from Southwark council to the Faraday Housing Association, a new subsidiary of the South London Family Housing Association.

The council received approval in principle for the stock transfer from the Department for Transport, Local Government and the Regions last Friday. However, government policy on social housing rents, to be implemented in 2003/4, is hampering the clear presentation of the case to residents.

Under the policy, the government wants to harmonise rents charged by social housing landlords for similar properties in the same geographical area over the next 10 years.

It also wants to set housing association rent increases at 0.5% above the retail prices index, which is expected to be less than salary inflation. A different formula will be applied to restructuring local authority housing rents.

A source at the South London Family Housing Association said: "The people who designed the new policy did not have stock transfers or New Deal for Communities projects in mind.

"The government's formula for fixing rents is very complicated, and it is still to be determined how the policy would apply to the Aylesbury Estate. We and Southwark council are still discussing it with them."

A source at the council said: "There are anomalies between the way the government wants to structure rent increases and the business plan.

"We are trying to understand whether the business plan for the Aylesbury fits with the government's financial model for stock transfer, and for showing the subsidy implications to residents."

The scheme will include four new neighbourhoods designed in a mix of architectural styles by Alsop Architects, Maccreanor Lavington, Paskin Kyriakides Sands and Cartwright Pickard Architects.