Hundreds of workers on the site of the new Hinkley C nuclear power station are staging a sit-in after a row over pay.
Some workers at the Somerset site, being built by French energy giant EDF, claim they have not been paid for days when snow stopped work last week.
Peter Hughes, South West Regional Secretary for the Unite union, said: "It is completely unacceptable for contractors Kier/Bam to decide not to pay its workforce while those workers remained available for work during last week's extreme weather and across the weekend. Unite understands that workers were told last Thursday during the working day to return to their lodgings.
"The union's members were due to work the weekend and were available to work although were instructed not to report for work due to the red weather warnings. On their return to site this week they were advised via text that they would not be paid Friday, Saturday and Sunday.
"The union continues to seek an acceptable and negotiated settlement to these issues".