One of the workers, who does not wish to be named, required skin grafts to both ankles following the incident at Stanley Road in East Sheen on 6 October 2010.

He and his colleague were left in severe discomfort after working as casual labourers for Geoffrey Cinko, 55, on a project to demolish five garages and erect two semi-detached homes in their place.

Westminster Magistrates’ Court heard during a two-day trial that the two injured workers had been asked to assist with the concreting of a basement excavation.

The wet concrete was poured into the excavation and they had to wade among it to evenly distribute and smooth the material before it was left to set.

Three hours into the job one of the workers complained of severe pain to his legs and left the concrete to try and wash the material off.

No adequate welfare facilities were available and Cinko instructed the worker to get back in the concrete and continue the distribution work.

The labourers continued working in varying depths of concrete up to just below their knees for at least another hour before they finished.

Both had to seek hospital treatment that evening after experiencing painful burning sensations around their ankles and lower legs.

They were diagnosed with chemical burns and were unable to return to work.

The HSE investigation found that neither worker was briefed on the risks of working with wet concrete, which is a strong alkali that can cause serious burns and ulcers.

Cinko also failed to provide personal protective equipment for the workers, such as boots providing cover to knee level; and welfare facilities at the site were totally inadequate.

Cinko, of East Sheen, SW14, was fined £10,000 and ordered to pay £10,000 in costs after being found guilty of safety breaches.

After the hearing, HSE inspector James Hickman said: “This was an entirely preventable incident that left two workers with serious and extremely painful chemical burn injuries.

“The risks associated with working with wet concrete are well known and the necessary control measures to protect workers are easily achievable.

“Yet they received no protection whatsoever from Mr Cinko, who showed a blatant disregard for their safety and welfare.

“He fell well short of the required standards expected of a competent principal contractor, and I hope his conviction sends a clear message to others.”