Leading UK sporting bodies are warning that they are unable to share crucial child protection information.
New figures given to the BBC reveal that 124 allegations of sexual abuse in sport were made last year.
There are fears that under the current system those accused can move to another sport or part of the country.
The Independent Safeguarding Authority says it is limited in the information it can share with sporting organisations.
Figures gathered by Brunel University show that of the 652 child protection issue cases examined by national governing bodies in 2011, almost a fifth involved allegations of sexual abuse.
Some led to criminal prosecutions but 98 were referred back to the sport by the police or children's services.
"They are the cases in which the sports are left in a kind of limbo about really knowing what to do," says Dr Daniel Rhind who carried out the research.
"Maybe there wasn't enough evidence or no chance of prosecution.
"Obviously there are the extreme cases of sexual abuse where it's clear-cut and it will go to the police, but slightly further down the line there are a lot more grey areas."
File on 4 can reveal a disciplinary hearing earlier this year found one of British judo's leading coaches was involved in abusing five athletes over 33 years. Until now the details of the hearing have not been made public.
Alan Roberts, who trained champions and Olympians, helped build the Dartford Judo Club, which is one of the leading sports facilities in the country.
A British Judo Association (BJA) panel decided that over a period spanning four decades, "he manipulated his position, influence and experience for the purposes of his own sexual gratification."
The finding was made on 'a balance of probabilities', which is a lower standard of proof than the standard used in criminal cases.
"He was found guilty of sexual assault on five individuals, two of whom were children under 16 at the time," says Scott McCarthy, the chief executive of the BJA.
"He has been banned from the BJA for life, he has been stripped of his membership and stripped of his coaching and that will keep him out of the British judo family forever."
One of the coach's victims, who started training with Alan Roberts when he was 17, revealed that he was indecently assaulted during lessons over a period of three years.
"I've not told my wife anything in depth - you keep getting reminded of what happened and you want to forget it," says David (not his real name).
The BBC understands that Alan Roberts is no longer involved in any form of coaching but he wrote to File on 4 saying he hopes to appeal against the judo association's ruling at some stage in the future.
"I have been the subject of conspiracy and spreading of malicious comment by several of the complainants," he said.
"Recently the BJA have been notified by eight very senior members of their concerns and individual experiences about untruthful comment and/or malice said to them concerning me, during the investigation."
The BJA has now made a referral to the Independent Safeguarding Authority (ISA), which gathers child protection information in England, Wales and Northern Ireland.
The ISA and Disclosure Scotland decide if someone should be barred from working with young people and vulnerable adults. Committing some crimes leads to an automatic ban, however other bars are at the authority's discretion.
The BBC has learnt that in 2010 and 2011 only 12 people from the sports sector were barred using the ISA's discretionary powers - that is around one in every 10 individuals referred to them during that two-year period.
However the ISA does not tell the organisation which made the referral what decision it reaches.
"I do think there is some more work to be done on how the ISA decides whether a sports organisation has a legitimate right to know," says Anne Tiivas of the Child Protection in Sport Unit, which was set up by the NSPCC and Sport England.
"Many sports bodies are making decisions for the whole of their sport.
"Knowing that individuals in sport will move across regions, move across counties and move across jobs, I think you could strongly argue the case that they have a legitimate reason to have that information."
The ISA also holds details of safeguarding concerns that would not lead to criminal prosecutions, including coaches having sex with 16 or 17-year-old athletes they are training.
Most sporting organisations ban such relationships and say having access to that information would be useful.
However the ISA says the current rules stop that from happening.
"I can't see any way at present we would be able to share that information," says Anne Hunter, the authority's director of operations.
And sporting associations say they are restricted from sharing what they know about coaches with other organisations because of data protection laws.
"If I've excluded a coach, I won't know if they've moved on to another sport," says David Sparkes, of the Amateur Sporting Association.
"If I do get to know I may in an anecdotal way tip someone off and say 'I think you may have a problem here'."
Both the ASA and the BJA believe a central body should be set up to gather and share information across sporting organisations.
They have also called for the government to examine whether people should need a licence to coach sports.
"I think parents would appreciate that," says Anne Hunter of the ISA.
"You can look up a plumber, to see if they're registered and whether they're equipped to do the job.
"So it wouldn't seem unreasonable that you could do that with a sport. I think that would be something that would be worth taking forward."