The Women's Sport and Fitness Foundation has claimed that overall, 81 per cent are doing too little exercise, with less than one in 10 young women playing any competitive sport.
However, according to WSFF, the problem is worsened by ideas that exercise is "masculine" and women don't like showing their bodies.
And if such trends continue, the Foundation has cautioned that in 2017, there would only be one in 20 women who will be doing enough exercise.
Culture and Sports Secretary Andy Burnham will be launching the Commission on the Future of Women's Sport, chaired by paralympian Dame Tanni Grey-Thompson, who will call for more cash and a higher profile for women's sports which get 50 times less media coverage than men's.
"I have seen for myself many of the inequalities that women and girls have to put up with in this country," The Mirror quoted her, as saying.
Sports minister Gerry Sutcliffe said: "We must challenge perceptions and get more women of all ages to give sport a try. Women's sport must get the media coverage it deserves."