Militants have put paid to plans for the National Union of Teachers to become a partner in a new education action zone, general secretary Doug McAvoy claimed this week.
The NUT can expect a fractious debate on action zones at its conference this weekend.
The debacle will allow left-wing members to underline their opposition to zones, which allow schools to be run by organisations such as charities and businesses.
A motion by Calderdale members says they "deplore any move by the union to become a partner, locally or nationally, and instructs the executive to ensure it doesn't happen again."
The NUT, led by Mr McAvoy, had begun negotiations with Oxfordshire council and an education charity about a zone covering the Blackbird Leys estate .
But Mr McAvoy admitted the early release of the news had scuppered the proposal. He denied there was any real split in the union and says he was only putting into practice union policy.