Unite has announced it has suspended Angela Rayner from her membership of the union, in an escalating row over the long-running bin strikes in Birmingham.
The deputy prime minister has been urging striking bin workers to accept a deal to end the dispute tabled by the Labour-run city council.
In an emergency motion at its conference in Brighton, the union said it would also re-examine its relationship with Labour if the council makes any of its members redundant.
Mountains of rubbish have been seen across the city since bin collection workers walked out in January, with an all-out strike going on since March.
A spokesperson for Rayner said she is no longer a member of the union – although Unite is insisting that she is on its membership system.
Unite is affiliated to Labour, and is the party’s biggest union funder.
It did not donate to the party’s election campaign last year, but made donations worth £10,000 towards Rayner’s campaign, according to her register of interests.
Members of Unite walked out in January over plans to downgrade some roles as part of the city council’s attempts to sort out its equal pay liabilities.
The dispute initially centred on the council’s decision to remove Waste Recycling and Collection Officer (WRCO) roles – which the union said would leave about 170 affected workers up to £8,000 a year worse off.
The council has disputed this, saying the maximum loss was be just over £6,000 and would only affect 17 workers, with pay protected for six months.
Unite has also urged the council to guarantee long-term pay for Grade 4 bin lorry drivers, claiming in April that bin lorry drivers’ pay could fall from £40,000 to £32,000 under new council plans.
An all-out indefinite strike was announced in March, and a deal to end industrial action has not yet been reached.
Conciliation service Acas has been mediating in the negotiations since May, but talks broke down on Wednesday, with council leader John Cotton saying the authority had “reached the absolute limit of what we can offer”.
Rayner, whose brief includes local government, has called on the union to accept a deal to end the strikes tabled by the city council, saying the authority had “moved significantly to meet the demands of the workers”.
In a statement, Unite general secretary Sharon Graham said the government’s backing for the council had been “disgraceful”.
“People up and down the country are asking whose side is the Labour government on, and coming up with the answer ‘not workers'” she added.
