Agency workers hired to fill the void in the wake of the Birmingham bin strikes have voted for strike action and will be joining the picket.
The first day of the action kicks off today, with a rally organised by the Unite union at the Smithfield depot in Birmingham.
The union said the numbers joining the strike were "growing daily" - but Birmingham City Council said just "a small number" of agency staff were taking part.
The replacement workers recruited by the Job&Talent agency, said they had voted in favour of industrial action "over bullying and harassment and the threat of blacklisting at the council's refuse department two weeks ago".
Sharon Graham, Unite's general secretary, said: "Birmingham council will only resolve this dispute when it stops the appalling treatment of its workforce.
"Agency workers have now joined with directly-employed staff to stand up against the massive injustices done to them."
Read more:
Six months on, there's no end in sight for the Birmingham bin strike
Birmingham bin strikes: How residents are taking action
She added: "Instead of wasting millions more of council taxpayers' money fighting a dispute it could settle justly for a fraction of the cost, the council needs to return to talks with Unite and put forward a fair deal for all bin workers.
"Strikes will not end until it does."
Strikes from the bin workers in Birmingham have been ongoing since January, and are likely to continue beyond May next year.
Birmingham City Council said it was "disappointed the dispute has not been resolved as Unite has rejected all our offers".
"We are continuing to make regular waste collections and our contingency plan is working," it added.
It also said it found "no blacklisting has taken place" after an investigation and that it "strongly" refuted Unite's claims of bullying, which it said were "unfounded".
Job&Talent has been contacted for comment.
(c) Sky News 2025: Agency staff covering for Birmingham bin strikers are going on strike
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