Striking workers at a Ministry of Defence (MoD) munitions site have raised concerns after a forklift truck driven by a soldier veered off the road.
GMB Scotland said it raises questions about employing military personnel to cover for staff on strike.
The workers are conducting an industrial action over pay at DM Beith in North Ayrshire.
The union said it informed staff a soldier was operating the forklift and it almost tipped over on Wednesday, September 13.
The accident prompted formal safety investigations.
But the GMB said the MoD declined to verify those involved despite confirming there were no injuries.
The complex, run by Defence Equipment & Support (DE&S), supplies weapons to the UK armed forces.
Chris Kennedy, GMB Scotland organiser, said: “It would appear this may have been a lucky escape but will they be so lucky next time?
“Our members have years of experience transporting sensitive material around the site and would rather be working than picketing.
“We have grave concerns about the kind of duties being undertaken by inexperienced personnel during this dispute, and for their safety and the safety of other workers.
“We would urge the Ministry of Defence to stand down the troops and start talking about a resolution.”
An MoD spokesperson said the soldier who operated the forklift was seasoned and licensed.
“No-one was injured”
They added: “An issue occurred last week at DM Beith when an unladen forklift truck’s wheel became stuck on wet grass when conducting a turn on a narrow road.
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“No-one was injured and at no point was the vehicle at risk of overturning.”
DM Beith provides weaponry to Ukraine during the ongoing conflict.
It has craft workers responsible for weapon assembly and non-craft workers tasked with transporting and loading arms for shipment.
The GMB said the wage gap between these two groups has tripled in recent years.
The strike, spanning two weeks, follows a four-day strike in the summer and the breakdown of negotiations at conciliation service Acas.