The employee was seen power washing the sloping roof while standing at the edge, without any safety precautions in place to stop him falling to the ground below.

The company was prosecuted by the Health and Safety Executive (HSE) following routine inspections in the town on 5 May 2010.

Halton Magistrates' Court in Runcorn heard the employee was photographed working nearly five metres above the ground on the roof of a semi-detached house in Lymm, Cheshire.

Inspectors immediately issued a prohibition notice, ordering the work to stop, until scaffolding, edge protection or other safety equipment had been provided.

The company was found guilty of breaching Regulation 4(1) of the Work at Height Regulations 2005 by failing to make sure the work was planned and carried out safely.

The company was fined £10,000 and ordered to pay prosecution costs of £7,269 on 14 March 2011.

Speaking after the hearing, a HSE Inspector said:

"It's incredible that workers were expected to power wash a roof while standing on it, without any scaffolding or edge protection to stop them falling.

"Working on a roof without safety precautions is dangerous enough, but the risk of falling was increased by the fact that moss and other detritus were being washed off the roof. One slip and the worker would have fallen to the ground, resulting in him being seriously injured or even killed.

"Falls from height are among the biggest causes of workplace deaths in the UK. Roofing firms should therefore ensure that they have safe systems of work in place to protect their employees and others."