The towers at the heart of Frank Gehry's controversial seafront housing and leisure development will have to be 12m higher than envisaged if the scheme is to go ahead.

Piers Gough, architectural adviser for the King Alfred project, said increasing their height was the only way of ensuring the surrounding low-rise buildings could be reduced in size - a stipulation of English Heritage and the Commission for Architecture and the Built Environment (CABE).

He said: "It's a play-off of lowering the perimeter buildings and raising the towers.

"We're not talking twice as high or half as much again - only a couple of floors.

"It's one of the ideas being considered by the team because I think CABE's letter, in particular, more or less advised us to do exactly that."

But Valerie Paynter of the lobby group Save Hove, said: "My heart sinks because they're not learning any lessons from what we have all been through in the last four years.

"Everyone has realised the council, architects and developers have bitten off more than they can chew.

"They need to understand they can't stuff all that on the site without it having a colossal impact on the community."

Mr Gough's idea would mean adding about 12m to the two towers - currently designed to stand at 75m and 60m.

Josh Arghiros, the managing director of Karis, the developer behind the King Alfred project, said: "Piers Gough has provided valuable advice to the project since its inception and has been hugely supportive throughout.

"We again welcome his views, which will be added to the professional opinion of all our advisers as we seek to resolve these final design issues.

"We want to maximise the number of affordable dwellings and secure the new sports centre facilities, while ensuring there is sufficient private residential accommodation to deliver all these benefits."

The plan, which includes a £48 million sports centre, has been dogged by opposition.

In April, the District Valuation Office, a wing of the Inland Revenue, said it was not financially viable and could run up to £29 million over budget.

Green party city councillors also withdrew their support for the plans.

Mr Gough said the final designs for the project might be completed within two weeks but would not be made public until the environmental assessment was completed, possibly as late as September.