DEVELOPERS will be told to dedicate almost a third of new housing projects to family homes, under new planning rules being drawn up by Southampton council chiefs.

But critics say the definition of a family home, which may include some flats, could see the policy fail to achieve its aims.

It is being suggested to counter fears the city is losing family housing to redevelopment and that new developments contain too few family homes.

Builders will still be able to "turn a profit" according to councillors, despite the policy potentially affecting projects as small as four units.

Latest figures show 95 per cent of all units built in the city over the past year were flats. Between 2000 and 2006 the figure was 87 per cent.

Tory council leaders will now rush through the new planning rules, insisting 30 per cent of any development is family housing.

The planning guidance, which will be approved in the spring, will also set out for the first time a definition for a family home and require "no net loss of family housing" in new proposals and conversions.

The document will become a "material consideration" for deciding planning applications.

Head of planning Andy Scate said coming up with the right definition would be a challenge.

He admitted two-bedroom flats could be considered family homes, but only if they have clearly defined amenity space, not just a balcony.