The Nature's Capital report highlights the importance of promoting green places for health and stresses the need for NHS and Primary Care Trust (PCT) funding to be allocated for green exercise prescriptions.
The National Trust's policy and campaigns officer Olivia Morris is the author of the "Access to Green Space for Health" section of the report. She said there is a growing recognition of the value of green spaces for well-being.
Morris said: "The increasing focus for many PCTs is on preventing health problems and there's the idea that doing exercise and going out to open spaces boosts well-being - for example, walking can reduce the risk of cardiac disease."
The National Trust has already teamed up with the Doncaster and Bassetlaw Primary Care Trusts and Bassetlaw District Council to provide guided health walks at Clumber Park, in north Nottinghamshire.
The aim of the initiative was to tackle the problem of obesity in the East Midlands, which has the highest number of obese women and second-highest number of obese men in the UK.
Morris added that only a small amount of funding was required for marketing the scheme in hospitals, GP surgeries, maternity units and libraries, as the National Trust provided the venue and walking guides.
The report points out significant cost savings for PCTs in recognising green exercise as a clinically valid treatment option for mental and physical health. Department of Health figures estimate a 10 per cent increase in adult physical activity would benefit the UK by £500m per year.
There is a growing movement to tackle health problems through green spaces. Natural England is leading a campaign that urges health professionals to make more use of the natural environment as part of the care they give to their patients.
The Royal Parks has also taken up the issue and provides walks in Regent's Park designed for people recovering from heart operations.