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 union said it would also re-examine its relationship with Labour after an emergency motion at its conference in Brighton.
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.
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.
Unite is a major donor to the Labour Party, and has previously donated to Rayner herself.
Members of the Unite union 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.
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 have broken down.
