The state of toilets and catering facilities at Runcorn Thermal Power Station has led to about 600 staff taking unofficial strike action every day since Monday.
The site is being built by main contractor Keppel Seghers for client Viridor Waste Management.
One worker, who asked not to be named, told the Liverpool Echo: “It is absolutely disgusting.
“There is a maximum of 12 toilets for 600 workers, while management have their own to use which are kept under lock and key.
“There is no hot water and they won’t even provide paper towels.
“I wouldn’t expect a dog to put up with the conditions at the site.
“We are being treated as second-class citizens.”
Staff involved include electricians, steel fabricators and insulation workers.
Talks were due to take place yesterday aimed at ending the dispute with the main contractor and four subcontractors.
Another worker said: “We have had monthly meetings where shop stewards have spoken to the management and promises have been made, but nothing is ever done.
“We came back in to work on Monday to find there was no electricity and all the toilets were locked up. It was the last straw and we felt we had to take action.”