Plans for a 40-storey skyscraper which would transform the seafront have been plunged into disarray by a legal challenge.

The 420ft block of apartments, dubbed the Roaring Forties, would be the centrepiece of a £175 million development dominating Brighton Marina and would be the tallest building in Sussex.

But it has emerged that an obscure transcript of a debate by MPs passing the Brighton Marina Act 1968 could derail Brunswick Developments' application for planning permission.

The Act states that nothing can be built at the marina taller than the height of the cliff.

The developer had expected to get around this by invoking a section which allows Brighton to vary the Act's terms if agreed with Brunswick Developments.

But campaigners have uncovered transcripts of Parliamentary debates when the Act was being formulated suggesting that the clause was only ever intended to allow the council to permit the construction of railings, lamp-posts, harbour lights and other elementary features promoting public safety.

The campaigners insist case law exists to show the spirit of Parliament has a material bearing on how an act should be implemented.

Derek Granger, chairman of the Kemp Town Society, said: "Before the Act there was great concern from people in Kemp Town that a marina would lead to the destruction of one of the finest conservation areas in England.

"This Act was meant to absolutely assure people that nothing would destroy their enjoyment of the sky, sea and views."

Almost 1,000 flats, 40 per cent of which would be low-cost housing, would be arranged in 11 buildings, ranging from five to 40 storeys.

Mr Granger said: "The vista towards the sea from the top of the eastern side of Lewes Crescent will be compromised. Instead of the last house being silhouetted against the sea and sky it will now be seen in the foreground of a modern block of flats.

"This gross overdevelopment will completely overwhelm the area. To entirely deny the whole intention of an Act of Parliament would be an absolute betrayal of the public will."

Peter Martin, deputy chairman of Brighton Marina Residents' Association, pointed out that the only reason private development was allowed in the first place was to finance the construction of the marina.

He said: "We now have a marina. There was no intention to go further than that. Irrespective of our concerns about overdevelopment, housing, infrastructure and transport, legally this development should not go ahead.

"The council and developers seem to be stretching the precise wording of an Act of Parliament without taking into account the spirit of the Act.

"The council should not bring this application forward to be determined until this has been sorted out."

Brunswick boss Andrew Goodall insisted the Act always envisaged the possibility there would come a time when buildings above the height of the cliffs were appropriate.

He said: "It was the Act's clear intention that at some point in the futureyou could build above the height of the cliffs. There is very little in Brighton that is built below the height of the cliff. Why should Brighton Marina be an exception?"