As a result, signing up to Unite the Union’s construction charter will now be a requirement for all City Hall building projects.

This will start with the St Ann’s hospital development project in Haringey, which was purchased by the mayor last year and will deliver hundreds of new homes.

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The charter states that subcontractors and building contractors under the control of local authorities must provide apprentice training, a safe working environment and the industry rate of pay to workers.

James Murray, deputy mayor for housing and residential development, said: “At City Hall, we are using all the resources and powers we have to build more council, social rented and other genuinely affordable homes. 

“The charter means that workers and residents can be confident that projects we are involved with will follow best practice on conditions and pay for construction workers, and I urge other authorities to join us.”