A third of British people are physically inactive and are putting themselves at increased risk of heart disease and other preventable illnesses, according to the British Heart Foundation (BHF).

More than 20m people in Britain do less than two and a half hours of moderate intensity physical activity each week as well as strength exercises on two days — the government defined threshold for physical inactivity.

The research found that these people are increasing their chances of developing cardiovascular diseases by 35%.

Mike Knapton from the BHF said a lack of voluntary exercise was "one of the most significant global health crises of the moment".

"Levels of physical inactivity and sedentary behaviour in the UK remain stubbornly high, and combined these two risk factors present a substantial threat to our cardiovascular health and risk of early death," he said.

The percentage of the UK population considered physically inactive varies from region to region, according to the BHF. Almost 50% of people in north west England and Northern Ireland do not do the minimum amount of exercise compared with just over 30% in south East England.

Some 40% of Londoners did not make the threshold — the same proportion of people putting their health at risk as those in the West Midlands and Yorkshire and the Humber.

BHF claim that the average man spends the equivalent of 78 days a year sitting down; a fifth of his life. Women spend a little less — 74 days a year — in a waking sedentary position.

The rise of physically inactive office jobs has been blamed for the rise in cardiovascular disease as well as people's recreational habits. Ofcom research found that the average UK adult watches 64 days of television each year.

Knapton said: "Making physical activity easier and more accessible for all is of paramount importance if we are to reduce the burden of inactivity-related ill health."

Research published in the European Journal of Preventive Cardiology in March found that insomnia could be linked to heart attacks and strokes.