Hundreds of construction workers at Ferrybridge power station in West Yorkshire have struck over safety.
The workers at the plant said a fire safety drill proved to be inadequate and many workers could not hear the alarm.
They believed there was a safety risk and walked off the site.
They were told the alarms would be replaced and they were asked to go back to work. But they were told they would not be paid for the remainder of the day.
According to workers on site there have been months of complaining about not hearing fire alarms on tests.
HZI Management now says the alarm system was adequate. But bosses have also added another eight sirens —taking the number from four to twelve.
One worker told Socialist Worker, “They then asked us to return to site to test the system and evacuate the site.
“We told them we wanted guarantees that we were going to be paid for the stand down time we had so far.
“They flat out refused saying we broke the national agreement by leaving the site.
“We are saying that they broke the national agreement by failing to upgrade the alarm system as the job progressed.
“Four sirens may have been adequate when the job began with just steel work in place but as the job grew it needed more coverage.”
Unite National official Bernard McAuley addressed the workers on Monday morning.
He said management was bringing in an independent safety adviser and recommended a return to work. The workers voted to stay out.