GPs are to be given national standards for "prescribing" exercise programmes for their patients.

Some doctors already refer patients for supervised courses at local gyms or leisure centres.

The aim of the standards, published by the Department of Health, are to improve the quality of existing schemes and encourage other doctors to follow suit.

The government hopes that the initiative will prevent people from developing coronary heart disease and rehabilitate those who have already suffered illness.

Patients who will be specifically targeted include those with

• coronary heart disease
• hypertension
• obesity
• diabetes
• mental health problems, including depression
• musculo-skeletal problems, such as chronic low-back pain
• problems caused by falls

The guidance will outline what exercise GPs should prescribe for their patients.

Swimming

At-risk patients will be able to get exercise such as swimming, aerobics and weight training on the NHS.

Experts have estimated that one third of deaths from coronary heart disease could be prevented if people started taking more exercise.

The NHS is there for people when they fall ill but it can do more to help people get well and stay well Alan Milburn, Health Secretary

GPs will be able to prescribe courses of exercise, and to negotiate bargain prices with local fitness centres.

They will also be encouraged to prescribe more gentle forms of exercise such as yoga for less active pensioners.

Some 300 exercise referral schemes are already up and running around the country.

The new national standards will help to identify patients for referral and the right scheme for them to be referred to.

Health Secretary Alan Milburn said: "The NHS is there for people when they fall ill but it can do more to help people get well and stay well.

"In the end prevention is better than cure. If we can help people do more physical exercise - especially when they are at risk of illness or recovering from it - we can cut the number of deaths from conditions like heart disease and stroke.

"This is not about telling people to take more exercise. It is about helping people to do it."

Andree Dean, Executive Chair of the Fitness Industry Association, welcomed the initiative.

"Exercise referral schemes provide great opportunities for fitness professionals to work in partnership with health professionals on schemes that target people who do not normally take exercise.

"These can make a real contribution to public health."

Experts recommend that people should try to be active for half an hour on five or more days of the week.

Surveys show that six out of ten men and seven in ten women are not active enough to benefit their health. Regular exercise can halve the risk of heart disease.