The number of homes in Brighton and Hove could grow by 12,000 during the next two decades.

A lack of green-field space means the increase would have to be achieved by the construction of tall, high-density blocks of flats.

The projected figure is contained in a Brighton and Hove City Council report ahead of a meeting to discuss house building targets.

If the actual number of new homes follows the projection it would amount to an average growth of 539 homes a year until 2026.

This is double the rate set out in the Structure Plan for 1991-2011, which envisaged growth slowing down to 260 new dwellings a year from 2006 to 2011.

Council leader Ken Bodfish said: "It's not a question of finding more space or spreading homes out. There isn't any green-field space the council can build on. We must use space and buildings more effectively."

A significant proportion of the extra homes may be provided by major developments planned for the Brighton Marina, Preston Barracks and the King Alfred site in Hove.

Mr Bodfish said increasing numbers of younger people wanted accommodation at an earlier age and the way families lived was changing and leading to a rising demand for more flats. Schemes like park-and-ride and strategies like the transport plan would bolster the city's infrastructure to withstand the pressures of a growing population, he added.

But Coun Anne Giebeler, a founding member of the No Inappropriate Development campaign, said continued expansion was bad for the city and questioned whether there would be enough people to fill new homes.

The independent councillor said: "You are going to knock down buildings and put up blocks of flats when there are already so many empty homes in the city."

Brighton and Hove City Council and East and West Sussex County Councils will learn how many more homes they will be expected to provide at a meeting of the South East England Regional Assembly on July 13, when draft targets will be set under the South East plan.