The government will close a "loophole" in the law that allows sports coaches and other people in positions of power to have sex with 16- and 17-year-olds in their care.
Thousands of people, including MPs, had backed a campaign for the Sexual Offences Act to be extended to cover any adult who has regular and direct contact with children and is in a position of authority over them.
Sports governing bodies, including British Gymnastics, Swim England and British Athletics, have supported the NSPCC's 'Close the Loophole' campaign.
The Positions of Trust law, which previously applied to roles such as teachers and social workers, will be extended as part of the Police, Crime, Sentencing and Courts Bill in Parliament on Tuesday.
Sports minister Nigel Huddleston told BBC Sport: "This is something many in sport have asked government to address, and it's right we close this loophole and ensure children are protected.
"Sport should be a wholly positive experience, and this draws a clear line in the sand that coaches must not have relationships with those they have a position of authority over, whether that's in a pool, on a pitch or a court. This will be strongly welcomed by sports governing bodies."
- More than 160 cases of coaches engaging in legal sexual activity with teens, FOI request shows
- Tanni Grey-Thompson supports sports coaches 'position of trust loophole' change
A Ministry of Justice statement said: "The move follows an extensive review which raised concerns that predators could exploit the particular influence these roles can often have in a young person's life - making them vulnerable to abuse."
Peter Wanless, NSPCC chief executive, said: "We are delighted that after relentless campaigning, the government has finally listened to our calls and agreed to close this legal loophole.
"This landmark step sends a clear message that children and young people can return to the extracurricular activities they love without being at risk of grooming by the very adults they should look to for support and guidance."