Staff at an Ayrshire nutrition plant have voted to continue strike action is a bitter dispute over pay.
Around 50 members of GMB Union at Royal DSM in North Dalry could continue their walk out for another five weeks after 80% backed another wave of strike action.
It comes as the repair and maintenance workers are involved in a fight over bonus payments detailed within national pay agreements for engineering and construction workers.
The union say contractors Altrad Babcock and Kaefer have so far refused to discuss the hourly bonus pay.
Industrial action started at 6am on April 18 for an initial three-week period.
A subsequent vote for an additional three weeks followed and, on Wednesday, a new ballot overwhelmingly backed another three-week wave of action.
This would take strikes into the middle of June.
The factory manufactures a range of vitamins for humans and animals with supplies to multinational brands including Coca-Cola, Berroca and Pantene.
More than 400 staff and around 150 to 200 contractors work at the plant.
GMB Scotland organiser Dominic Pritchard said: “It was not our choice to have this dispute and it would not have been necessary if these two firms had engaged with us in any meaningful way.
“Our members are due these bonus payments and, as a matter of principle, are ready to fight for them.
“Their refusal to do so seems short-sighted and has led to an industrial action which will undoubtedly be impacting on the good-running of the plant.
“The vote to continue this strike for up to nine weeks is only one signal of the strength of will of our members and sends a message to managers to review their current position and allow negotiations to begin.”
A spokesperson for Kaefer said: “We confirm that Kaefer employees contracted to work at the Royal DSM plant in North Dalry are among those workers participating in industrial action.
“We continue to support constructive dialogue between GMB Scotland, Unite the union, and Kaefer to reach a mutually acceptable resolution.
“The safety of our teams remains paramount and will not be affected by any potential industrial action.”
STV News has contacted contractors Altrad Babcock for comment.
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