Staff at several power plants in Fife and East Lothian have walked out on wildcat strikes.
Scottish Power confirmed that none of their employees is taking part in the action - only contractors hired to work on-site.
Power supplies will also not be affected by the unofficial action.
Unions claimed around 250 workers at the Longannet power station in Fife had abandoned their work to protest the outcome of an industrial relations dispute in England.
The wildcat strikers object to events at the Lindsey Oil Refinery in Lincolnshire, where 647 workers were dismissed for staging their own wildcat strike over a jobs dispute.
Contractors at Cockenzie in East Lothian and Shell's petrochemical plant at Mossmoran have now joined the secondary action.
One worker said: "I believe you've got to stick together and be as one. It could be us next, you know what I mean."
Another claimed: "It's a case of divide and conquer; you've got to be seen to be sticking together."
The employees refusing to work are all contracted to carry out maintenance at the power station over the summer months.
Their union UNITE said it does not support wildcat action but it sympathised with the strikers.
Scott Foley from UNITE told STV News: "Whilst the union can not support unlawful industrial action they do sympathise with the predicament of our workers who work in engineering construction.
"They work differently from most other people and they work in an environment where there’s close camaraderie between each other. They work alongside each other on different projects across the UK. They know each other and I think the difficulty in trying to get the members to remain at work is that there is that close camaraderie."
Workers will be holding a mass meeting outside the gates of the plant at 7.30am on Wednesday morning to decide their next move.
