Mr Laing has several other sites in mind, including Docklands, King's Cross and the South Bank, 'close to the tourist and entertainment circuit' of London. The move could be seen as an attempt to step up pressure on zoo leaders to opt for the Laing plan.
He has the support of Sir David Attenborough, the naturalist and broadcaster, who said: 'It would be a tremendous attraction to everybody. It would also be a way of maintaining contact with the excitement and drama of the natural world without any of the problems that make zoos aesthetically and morally objectionable to many.'
A multi-million pound hi-tech aquarium in Britain would 'teach an increasingly urbanised population about the natural world', Sir David told a meeting of the British Association for the Advancement of Science in Plymouth last month.
'He has been to see us and will support us,' Mr Laing said. Sir David emphasised, however, that he would not do anything that he thought was contrary to the best interests of London Zoo.
'I would be delighted to see an aquarium in London, particularly within half a mile of Madame Tussaud's, which gets so many visitors. It's the kind of facility this country ought to have and it's certainly very terrible that it hasn't,' he said.
Mr Laing said his consortium's work on securing financiers and drawing up plans for an aquarium 'cannot go to waste'.
'We have asked in the Docklands. They were responsive, but we are not sure it's right for us,' Mr Laing said. Part of the appeal of London Zoo was that it already attracted a million visitors a year. 'It's a brilliant leisure site which is capable of doing a brilliant job.'
The aquarium is the centrepiece of the Laing plan for London Zoo, and is seen as the largest potential money-spinner for the site. Similar aquariums in Boston, New Orleans and Tokyo are hugely successful.
Mr Laing's consortium, New Zoo Developments (NZD), set up to draw up financial and development plans for the Regent's Park site, has been in touch with several developers about alternative sites.
Officials at the zoo are also considering three other bids, one from management and two put together by zoo staff. All have far more modest budgets than NZD.
Mr Laing said the other plans had much to offer, but were less financially sound. He doubted whether any of the other proposals could raise sufficient funds to pay for the zoo's maintenance and running costs.