WORK was stopped last week on the £350 million Bluewater project in Kent because of 'appalling' site conditions.
Health and Safety Executive (HSE) inspectors stepped in to protect builders forced to work in the dark.
The site was also swamped with mud and workers had no hot water to wash themselves with.
Five prohibition orders were imposed, one each on subcontractors Lester Rose Builders, O'Rourke Civil Engineering, Baco Contracts, English Architectural Glazing and John Martin Construction.
They were forced to stop work for a day until adequate lighting was installed.
An HSE spokesman said: 'There were people working up high without proper lighting. It was incredibly dangerous.'
One worker said conditions on the former quarry site were 'appalling'.
He said: 'It is a big mud hole and we are wallowing around like hippos in the freezing cold. At the end of the day there is not even any hot water to clean up.'
The HSE said it was writing to Bovis about the welfare conditions on the site.
A spokesman for construction manager Bovis said the hot water supply had been interrupted by vandalism and that problems with the lighting were the responsibility of the subcontractors.
He dismissed complaints about mud on the site: 'Actually the site is extremely well drained. The problems with mud are no worse than on any other site.'
The HSE was called in by safety representatives from the committee of trade union representatives.
A spokesman for the committee said there were not even proper toilet seats for the project's 1,600 workers.
He said: 'Working here is unquestionably an unhealthy experience. It is damp and cold. There is no effort to give the men a decent and clean working environment.
'It is the worst site I have seen. We've got to get hot running water and some proper toilet seats.'
O'Rourke spokesman John Flavin said the problem had been dealt with immediately and Baco Contracts spokesman