Birmingham refuse collectors have voted to reject the council’s latest offer in the long-running dispute over pay and contracts.

The bin workers have staged strikes and also been working to rule for several weeks over a pay dispute which unions said would see them lose £4,000 each per year. The latest strike was called off on 12 January for further talks. But after the amended offer resulting from the talks was rejected by 95 per cent of the 500 workers, further strike action is imminent.

The dispute in Birmingham centers on the legal duty of UK councils to ensure equal pay for men and women, and the method the council used to achieve this.

The row erupted after the council tried to backtrack on gender pay equality enhancements worth about £4000 per year. In 2010 a court ruled that this action was incorrect or “not equality proofed”. Now the council has said it needs to remove the enhancement, which has the effect of reducing pay.

But the GMB and Unite unions representing workers are unhappy that the current pay review will mean that workers such as refuse collectors, garage staff and road sweepers will suffer a pay cut, and has accused the council of ignoring union advice when it made its original decision.

It is understood that the latest offer from the council involved a more generous deal for workers on overtime, but made no concession on basic pay, which the unions see as the central issue.

The council said in a statement: “There is disappointment that despite several weeks of intensive and constructive talks between the council and the trades unions, the unions and their members have rejected the proposals which resulted from these talks.

Unite’s regional secretary, Gerard Coyne accused the council of “wasting taxpayers’ money by pretending to negotiate for a month”.

Unison assistant general secretary Roger McKenzie added: “The workforce is frustrated and feelings are running high. At a time of economic uncertainty and unprecedented public spending cuts, members feel like they are not being treated with respect.