Unrest among RIBA staff about Phillips' candidacy was already high before his extraordinary revelation on Wednesday evening that he was a member of the right-wing political group.
Phillips is believed to have made at least one formal complaint about a senior administrator during his time as a national councillor.
He also angered staff after publishing a savage critique of the 2004 report Why Women Leave Architecture.
But after his BNP admission, discontent at the possibility of him winning the election has apparently reached new levels.
The source told the AJ that some members of staff have informally discussed the possibility of a mass resignation, insisting there is no way they would work for him.