One worker said: “It’s an absolute joke down there – how can you run a major project like this making people walk for two miles to use the loo?

“We haven’t had a mobile toilet in the tunnel down here for weeks now.

“We have to walk all the way to Tottenham Court Road which is two miles away.”

Workers are also unhappy about a lack of canteens and a site access system described as “chaotic”.

Another source said: “There’s only one turnstile to get on site in some places so the queues are chaotic.

“You have to leave early to try and beat the rush and lose out pay wise.”

Construction union UCATT is planning a demonstration at the Fisher Street site tomorrow while Unite leaders are set for a showdown meeting next month with Crossrail chiefs and contractors over bonus pay demands by electricians.

Contractors are understood to have set up a series of working groups to address the issues before the situation escalates.

But rank and file sparks are known to be organising on the job and are planning to produce their own site newspaper.

Tunnel Vision will be widely circulated among the workforce and detail ongoing disputes and demands.