The work would include ripping out the concrete walkways, once described by the architectural historian Sir Nikolaus Pevsner as 'a thrilling experience if the weather is fine' but which have become a haven for skateboarders and the homeless.
While maintaining that it would still like, in conjunction with Stanhope Properties, to replace two concert halls on the site - the Purcell Room and the Queen Elizabeth Hall - with shops, offices and new leisure buildings, the board privately acknowledges that it 'can no longer plan to upgrade our facilities using the profits from commercial development'.
A confidential memo to the chief executive, Nicholas Snowman, and the chairman, Sir Brian Corby, says: 'There is no longer any prospect of our being able to find a way ahead that does not make any call on the public purse. Our resources are insufficent to enable us to maintain the current buildings, especially the Royal Festival Hall, to the proper standard. Something must be done and done soon.'
Under its new plan, despite the Hayward reprieve, the board wants to build a pounds 40m gallery on the car-park site next to the riverside Jubilee Gardens. However, this is one of several London locations being considered by the Tate Gallery for a new Museum of Modern Art.
Nicholas Serota, the Tate's director, told the Independent on Sunday: 'The South Bank is well located and it is a place that people are drawn to. Our prime consideration is good public transport. We've lived for 100 years on the 88 bus route, and we think it's time we did better'.
Both the board and the Tate see a new gallery on the site as a millennium project, and will be making an early call on the new national lottery funds.
Since the demolition of the Hayward was first proposed in the architect Terry Farrell's masterplan, barely any money has been spent on the gallery. Mr Serota said: 'I think it's suffered from neglect and is clearly in need of restoration and renovation.'
Andrew Dempsey, the Hayward's deputy director, said: 'As long as we felt the other scheme was possible, nothing was done. Now that the grand scheme is not viable, what can be done to improve the Hayward will be done and as far as I'm concerned that's a welcome focus.'