The Railway Inspectorate is investigating an accident where a scaffolder narrowly escaped death after being hit by a 25 000 V cable while working in an area where the electricity supply was supposed to have been cut.

The accident happened on the City of London Broadgate project near Liverpool Street Station. A spokesperson for steelwork contractor Kvaerner Cleveland Bridge, the scaffolder’s employer, said Railtrack had given “rail possession” to the contractor to allow work to be carried out.

In rail maintenance work, “rail possession” means Railtrack has cut the electrical supply to a designated area to allow contractors access to carry out work. Kvaerner claims it is in possession of an isolation certificate that it would have handed back to Railtrack once work was finished. Railtrack said Kvaerner did hand back possession of the line and that it reinstated the electricity supply. This was 10 minutes before the incident.

Vince Keen, 60, is currently in the intensive care unit of the specialist burns unit at Chelmsford Hospital. A spokesman for the Health and Safety Executive, which is also involved in the investigation, said the worker suffered 40% burns, a collapsed lung and a fractured skull after the impact of the voltage threw him through the air.

Workers on the site stopped work following a meeting on Tuesday because, a site source said, their confidence in the safety procedures had been “shattered”. The source said: “If the power was on there, it could be on anywhere.”

Engineering union AEEU was due to visit the project on Wednesday to hold discussions with Kvaerner Cleveland Bridge and construction manager Bovis.