Stafford Magistrates’ Court heard that contractor Colin Boon, 55, of Stoke-on-Trent, was in charge of a gang of road workers sealing a pavement on Wilson Road in the Hanford area of the city on 13 September 2012.

The victim, a 36-year-old worker from Stoke-on-Trent, slipped as he climbed from a flat-bed lorry which was next to the mixer.

He put his left leg down to steady himself but it went through the unguarded opening of the mixer. The moving paddles in the mixer severely injured his lower left leg, resulting in amputation below the knee.

An HSE investigation found the guard over the rotating paddles in the petrol-powered mixer had been removed the day before the incident and not replaced.

The man was in hospital for two weeks and eventually returned to work for the same employer, but has since moved job because of difficulties with mobility.

Boon pleaded guilty at an earlier hearing to a safety breach and was fined £6,700 and ordered to pay £8,000 in costs.

Speaking after the hearing, HSE inspector Alastair Choudhury said: “This was an entirely preventable incident and a young man has sustained an injury that will have a huge impact on the rest of his life.

“Colin Boon failed in his duties to these workers. He was aware the guard had been removed and took no action to prevent use of the machine on the 13 September 2013.

“Guarding on machinery is there for a reason – to prevent people getting hurt. If it is removed, absent or defective, employers are putting employees and others at risk of injury or death.

“No commercial pressure to take these risks is justified and the potential costs of incidents far outweigh any savings in time or money.

“The mixer should not have been used once the guard had been removed.”