Almost half of Britons are unwilling to walk for 20 minutes, new research has revealed.
One in two claim to be worried about exercise, yet 45% will take public transport instead of a short stroll, a charity found.
The research by Living Streets suggested that a five minute walk was all it would take for one in 20 Britons to use transport instead of making the journey on foot.
Around three quarters (76%) of those polled were oblivious to the Government's recommendations that adults should carry out 150 minutes of exercise each week.
Living Streets is launching a 'Try20' campaign which hopes to target middle-aged adults, urging them to try walking for 20 minutes a day in May, which has been designated National Walking Month.
A short walk every day can lower the risk of developing a range of diseases, the charity said.
One in four people (24%) surveyed said there was nothing stopping them from doing more exercise, with one in 17 claiming they "couldn't be bothered" to be more active.
The research also suggested that there were fears around exercise, particularly among women.
Twice as many women as men said they were "very worried" about their fitness levels.
Joe Irvin, chief executive of Living Streets, said: "Our findings show that, worryingly, for many people there is an unwillingness to make short journeys on foot and instead a readiness to sit behind the wheel, which is not only bad for our health and finances, but also the environment.
He urged people to take part in the new campaign by making "small changes" to daily routines.
"By skipping a stop on public transport or parking further away, we can all reduce the risk of significant health issues including heart disease, cancer, depression and type 2 diabetes as well as getting fitter and happier in the process."
Dr Penny Woods, chief executive of the British Lung Foundation, said: "It's important for everyone, including those with lung conditions, to be regularly physically active. Walking can be a great way to keep fit and socialise, and many health care professionals and local councils can offer advice on local walks and exercise schemes.
"Making some of these shorter trips by foot instead of by car would have the health benefit of helping keep you fit, and reduce the amount of harmful pollution released into the air."