English Heritage (EH) is on the verge of abolishing the Grade II* rating from the listing system, the AJ can exclusively reveal.
The move, which will shock members of both the architectural and conservation communities, will more than double the number of Grade I-listed buildings in England and Wales.
It is understood that EH is planning to bump up all buildings that are currently listed at II* to Grade I. This would mean that the number of landmarks with the highest statutory protection would increase from 3 per cent of all those listed to 7 per cent.
However, some observers from the conservation sector have warned that EH is also considering plans to relegate a limited number of the younger II* buildings - likely to be Modern 20th-century sites - down to Grade II.
Alarm bells would be set ringing for fans of the Modern Movement if this was adopted as policy. Examples currently at II* level include David du Rieu Aberdeen's TUC Congress building in central London, and Denys Lasdun's ziggurat accommodation blocks at the University of East Anglia.
While the move to wind up the ranking remains in an EH consultation document called the Heritage Protection Review, which will be finalised in early summer, one senior source in the organisation said he would be 'extremely surprised' if it didn't eventually make it in to the statute book.
The motivation behind the proposal is not yet fully clear, but it is understood that EH has come under pressure from its sponsoring government department, the Department for Culture, Media and Sport, to simplify the listing system and so ease public understanding.
Matthew Slocombe, a deputy secretary of the Society for the Protection of Ancient Buildings, said the policy came as a surprise to conservationists. 'This did rather come out of the blue, ' he told the AJ. 'We were surprised about it as there has not been any publicity about it.
'As I understand it, there is every likelihood that some of the more recent Grade II* buildings may well find themselves back in the Grade II category, and I can see why fans of the Modern Movement would be worried about this.'
But Catherine Croft, director at the Twentieth Century Society, said that she would wait to see what the final proposals are before sounding the alarm. 'In general, we support all plans that increase protection, ' she said.
'This plan could make things marginally better, ' she added. 'But if they choose to chuck out a load of Grade II*-listed buildings, then this would obviously be a major reason for concern.'