But the union says making resources available to the group is illegal and conflicts with its own rules.
General secretary Rodney Bickerstaffe wrote to branches in December advising them of national executive committee guidance that no union funds or resources, including staff, should be made available to the Campaign for a Fighting and Democratic Unison.
The group had close links with the Socialist Party, and although members were free to join as individuals, union resources could not be used by it, he said.
He said the group aimed to win control of the union back from full-time officials, and called on members to support an activists' conference in March.
A Unison spokeswoman said there was no vendetta, but counsel had advised the NEC last year that it was illegal for union resources to be used by the CFDU.