Women in Sport is run by alumna Stephanie Hilborne, class of 1986, who is the charity’s chief executive.  She said: "It's an absolute travesty that teenage girls are being pushed out of sport at such a scale.

"Teenage girls are not voluntarily leaving sport, they are being pushed out as a consequence of deep-rooted gender stereotypes. We must all do more to reverse this trend and not continue to accept this as inevitable."

The survey of 4,000 teenagers, funded by Sport England, reveals that the reasons include body image, puberty and fear of judgement. The charity says it’s a myth that girls drop sport simply because their priorities change.  It has urged the sport, leisure and education sectors to work harder.

Half said they disliked being watched if they exercised, and some seven in 10 avoided sport on their period.

Other reasons included:

• Lack of confidence (61%),
• Schoolwork pressures (47%)
• Feeling unsafe outdoors (43%)

Feeling self-conscious in gym or sports gear was another worry. Some said they did not "have the right body shape", while others dislike becoming hot and sweaty. Sport became too competitive as they grew older, some said, and they no longer felt able to join in just for fun.

Asked what would motivate them, many said making exercise more fun, with more opportunities outside school with friends.