Architects RMJM and Enric Miralles' practice EMBT are expected to face major criticism later this month when Lord Fraser publishes his report into the massive cost and time overruns on the Scottish Parliament.
RMJM's Edinburgh office has confirmed that the Tory peer has sent its principal Brian Stewart a letter warning him he will be found to be at fault when the report finally goes public.
A spokesman for the firm admitted it had received the letter, but insisted Stewart would be using his legal right to reply.
The AJ also understands that both Miralles' Barcelona-based widow Benedetta Tagliabue (the sole boss of the firm) and the Scottish office's former chief architect Bill Armstrong have also received similar letters.
The letters represent the last phase in the inquiry's development. The warnings were sent at the end of last week to anyone found to be at fault for the Holyrood debacle in the report's final draft. All involved have the right to reply before the official publication later this month.