A group of London property developers is in talks with Westminster council over creating a land bank of sites for affordable housing.

However, opponents of the proposal say it will create ghettos of social housing in poor areas rather than promoting mixed-tenure communities on higher value sites.

Guthrie McKie, the Labour housing spokesman at Westminster council, said the plans smacked of “social apartheid”.

Under the plan, developers could give the council cash and land in return for planning permission if they agreed it would not be viable to build social housing alongside private units.

The Westminster Property Owners Association, whose members include the Peabody Trust, believes the land bank will speed up development of affordable homes.

Dickon Robinson, Peabody’s director of development and technical services, said the land bank would not create social exclusion.

He said: “When developers talk to us we say we wouldn’t be interested in taking small numbers of homes because Peabody is a manager of estates. We think it’s more efficient and that’s a big issue for associations.”

He said the scheme would be useful for small private developments that would provide only a small number of social homes.

The social housing requirement for several private sites could be added together onto one landbanked plot. Developers would be able to charge more for their original plot – which would not contain social housing – and so would have to make a greater contribution to the social housing plot and therefore more homes could be built.

Peter Rogers, chief executive of Westminster council, insisted the council would continue to push developers to provide social housing alongside homes for sale.

However, he said the land bank plan could help to speed up the provision of social housing. He added: “Our presumption is for on-site [mixed-tenure] development.

“We wouldn’t like developers to think they can get away with just throwing cash at us.”

He emphasised that discussions with the Westminster Property Owners Association were at a very early stage and no decision had been made on the proposal.

The council’s overview and scrutiny panel is likely to consider the proposal and alternatives.