Workers helping to construct Bingley relief road have been told to cover-up or face disciplinary action.

The move by contractors Amec is to safeguard the workers from the harmful effects of the sun's rays as the hot weather kicks in.

James Weekley, spokesman for Amec said: "There are minimum clothing requirements, long trousers and a long sleeve shirt, and we provide personal protective equipment that workers are required to wear.

"It is going to make them hot but its more important that they're safe and visible."

The number of skin cancer patients in Bradford has risen by more than 20 per cent in the past few years, with more than 10,000 people attending St Luke's Hospital with skin-related problems.

Other firms are also giving their employees advice against the potentially cancerous effects of the sun's radiation.

Michael Lee, manager of Leeway Building Contractors, is among bosses who are supplying sun cream to protect their workers.

"Health and safety is an important factor and a very big part of our business. Buying a bit of sun screen is not a big price to pay for the safety of our workers," he said.

Another Bradford firm, HB projects Ltd, has also made funds available for staff to buy sun cream.

Employers now have a legal duty to protect outdoor workers from the hazards of the sun and could face fines of up to £20,000 or even a prison sentence if they don't comply.

The Health and Safety Executive carries out spot checks to make sure bosses are following safety guidelines but some businesses are taking the risks less seriously than others.

Department of Trade and Industry spokesman David Hands said: "Firms could probably do more. A lot of people know the dangers but when it gets hot people tend to forget about it."

The Transport and General Workers' Union is reminding bosses of their duty to keep workers safe in the sun.

A T&G spokesman said: "When you are working in the elements there is a responsibility on the employers to provide the appropriate protection. At the end of the day there has got to be sensible work policy and sensible implementation of that policy."