This latest twist in the borough’s fractious politics came after Martin Winter claimed senior Labour councillors and council officers had conspired to remove him.
Mr Winter formed a separate political group with Labour councillors Stuart Exelby and Eva Hughes, the only two surviving cabinet members, though Cllr Hughes subsequently rejoined Labour.
A Yorkshire & Humberside Labour Party spokesperson said Mr Winter and Cllr Exelby had failed to register as Labour group members by a 25 May deadline.
“The matter has now been referred to the Labour Party’s constitutional officer, who will advise them that by leaving Doncaster Labour group they are deemed to have auto-expelled themselves from the Labour Party,” the spokesman said.
But Mr Winter said: “Stuart and I do not wish to leave the Labour Party, nor do we consider our actions lightly or hysterically. As of [29 May] we have not been notified officially of any action by the party.”
The council’s latest bout of infighting erupted after an Audit Commission report on the ousting of former managing director Susan Law in February 2007 (LGC, 22 May).
Mr Winter said the report described “appalling behaviour” by some senior Labour figures in the town and called on the party to intervene.