Around 1,200 electricity workers are to be balloted for strikes in a dispute over working practices, terms and conditions.
Union members at Scottish Power in Scotland, North West England and North Wales will vote in the coming weeks on whether to support a campaign of action.
The result will be known on May 14. Unions say the dispute is about enforced changes to working practices and terms and conditions of workers who carry out repairs to disrupted power supplies from substations and at the roadside both for domestic and business needs.
Albie McGuigan, of the GMB, said: “Members have now been under attack from Scottish Power for a number of months and although we have attempted to reach an amicable compromise with the company, we have been unable to do so. At present, the workers are complying with their obligations to provide a professional service for customers – but their patience is now at breaking point.
“GMB remains steadfast in defending our members’ terms and conditions. The Scottish Power workers are at the front-line of maintaining power supplies and are outraged that long-standing, successful working practices are threatened in this way.”