One in six young runaways helped by Barnardo's has been sexually exploited, the charity has revealed.
It said victims were often groomed by pimps and moved around the country to be sold to clients.
A 2005 report showed as many as 100,000 youngsters under the age of 16 go missing
every year in Britain - equal to one every five minutes.
Many end up staying with friends, but others end up in far riskier situations, the charity found.
Children who repeatedly go missing are in grave danger of falling victim to those who prey upon them for sexual and financial gain.
One parent told Sky News her daughter began to regularly go missing aged just 12. She would return home with mobile phones and lavish gifts.
"When I asked where they'd come from she would just say 'friends'," said Sharon, which is not her real name.
The "friend" was actually a pimp. Sharon said her daughter was forcibly hooked on cocaine and cannabis and then groomed into prostitution. She was then driven to different cities for sex.
"I have phone video of her being raped by three men and she looks drugged to me," Sharon said. "It's something that will live with me for the rest of my life."
Barnardo's is so concerned it has launched a nationwide campaign to raise £1.3m ($2.8m) to fund 21 specialist centres helping victims of sexual exploitation.
The charity is also calling on the Government's Missing Persons Taskforce to make sure it sets out clear measures to deal with the problem.
It also wants the Child Exploitation and Online Protection Centre to urgently address the link between missing children and sexual exploitation.
"Children who repeatedly go missing are in grave danger of falling victim to those who prey upon them for sexual and financial gain," the charity's chief executive Martin Narey said.
"For Barnardo's staff identifying those children at risk of sexual exploitation is half the battle, we need to get to these vulnerable children first."
A fundraising appeal voiced by Dame Helen Mirren starts today.
