Less than half of GPs currently have access to an exercise referral scheme, due partly to a lack of understanding of the initiative.

A survey by the Mental Health Foundation (MHF) has found that there are "significant barriers" preventing patients from accessing exercise on prescription.

The report mentions funding constraints within local government and primary care trusts as one of the most significant issues facing the scheme, but also identifies a lack of recognition of the scheme's benefits as a threat.

The report, called Moving on Up, states that there is currently a significant lack of awareness of exercise schemes amongst GPs and other healthcare professionals who might refer patients.

Of the GPs who have access to a referral scheme, however, nearly 80 per cent use it on a regular basis.

In the report, MHF makes a number of recommendations to encounter the barriers to referrals. These include Primary Care Trusts funding the development of a range of exercise activities; healthcare professionals and exercise staff working in referral schemes developing closer working links; and a variety of exercise activities to be offered by providers, in addition to gym-based programmes, to cater for patients' different interests and levels of fitness.

Commenting on the report's results, Central YMCA's CEO, Rosi Prescott, said: "Despite the increasing evidence base to support exercise schemes, much more needs to be done to persuade those in the health service of their benefits.

"Although the number of GPs who would prescribe exercise is increasing, it is disappointing that it remains so low. More needs to be done to ensure that all people working within primary care have access to exercise referral schemes - there should be no postcode lottery."

Andrew McCulloch, chief executive of MHF, added: "Exercise therapy is an effective, clinically approved treatment option that can help treat mild to moderate depression, yet this report tells us of the barriers that must be overcome before GPs in all parts of the country can offer exercise on prescription to patients experiencing the illness."