According to a document seen by the AJ, fears are growing that architects will not be able to receive English Heritage's grant-aid handouts without being on the AABC list.
More worryingly, there are concerns that the number of government organisations demanding the architects they employ are AABC accredited could balloon.
The leaked complaint also raises issues about how smaller practices and sole practitioners are struggling to get onto the register.
Currently the AABC, under the authority of the RIBA, requires architects to have completed at least five conservation jobs in the last five years.
For some practices - particularly those who are involved in long, one-off projects - these criteria are becoming increasingly hard to meet and this, says the document, is damaging the number of architects entering the field.
An initial response to the allegations is expected from the OFT within the next few weeks.