Gary Glitter, jailed in Vietnam, is one of the UK's most infamous sex tourists
The government is "turning a blind eye" to British sex tourists and failing to prevent abuse despite having laws in place for 10 years, claims a charity.
The Home Office said the UK had tough laws but children's charity Ecpat UK wants an overhaul of the way Britain deals with nationals convicted abroad.
It wants offenders returned to the UK, put on the sex offenders register, and in some cases have travel restricted.
Gary Glitter is due to be freed from a Vietnamese jail and deported to the UK.
The report from the children's rights charity comes ahead of the ex-pop star being deported by the Vietnamese government after serving 27 months in prison for child molestation.
The 64-year-old, whose real name is Paul Francis Gadd, was convicted in 2006 for molesting two Vietnamese girls aged 11 and 12.
They go from one country to the next or they may stay underground in the first country where the offence has taken place - we lose track of them
Christine Beddoe Ecpat
He had his three-year sentence cut last year under a national amnesty, and is due to be sent back to Britain on Tuesday. He will then be interviewed by UK police and required to sign the sex offenders' register.
But Ecpat said tools to protect children were not being used fully by the British authorities, with only five sex offenders prosecuted for abuse abroad since 1997.
It said this compared with more than 65 prosecutions by US authorities and over 25 by Australian authorities.
The charity - which campaigns against the commercial sexual exploitation of children - said between 2006 and 2008 at least 15 British nationals were charged in Thailand alone for the sexual abuse of children.
And others have been prosecuted in India, Ghana, Vietnam, Cambodia, and Albania. Many had been teachers or volunteers in orphanages, said Epcat.
ECPAT's Christine Beddoe explains the charity's concerns
Ministers should return offenders to the UK immediately after sentencing so they can be placed on the sex offenders register, risk-assessed and managed, said the report.
Director of Ecpat Christine Beddoe said it was often only cases involving celebrities that caught public attention, and that it was too easy for abusers to stay off the radar of British police.
"The biggest problem is in the twilight zone of international jurisdictions when offenders don't come back to the UK immediately. They go from one country to the next or they may stay underground in the first country where the offence has taken place. We lose track of them."
The report also said future foreign travel should be restricted, where appropriate.
The charity argued Foreign Travel Orders (FTO) - civil orders developed to restrict the travel by UK registered sex offenders - had not been used enough.
An FTO requires an offender to notify police if he or she intends to travel and the information is shared with police at the destination.
If there is evidence an offender intends to commit an offence abroad they can prevent them from visiting that country or travelling at all.
The Home Office said five FTOs were granted between 2004/5 and 2006/7.
More than 3,000 similar bans have been issued to prevent football hooligans travelling.
Ecpat's report also made the following recommendations:
• The UK should develop stronger bilateral co-operation relationships with relevant countries.
• Joint investigation teams should be developed with other national law enforcement agencies.
• Agreements with foreign governments should be constructed to deport and chaperone convicted offenders back to the UK, to be placed on the Sex Offenders Register.
Meanwhile, the Home Office said while more could always be done to keep children safe, the UK had "some of the toughest laws in the world".
It added that a recent change to the law meant those who commit sex offences against children abroad now faced prosecution in the UK.
Ecpat said it was too easy for offenders to stay off the radar of UK police
This "sends a strong message to so-called sex-tourists that they won't get away with targeting other countries with less strict controls than the UK," said the Home Office spokesman.
"From the autumn, we also intend to make registered sex offenders notify the police of any travel abroad."
They added that Britain had recently signed the Council of Europe's Convention on the Protection of Children from Sexual Exploitation and Abuse, "which sets standards to ensure that countries criminalise the sexual exploitation and abuse of children".
Last month new rules came into force which meant that British "sex tourists" who abuse children abroad could face prosecution in the UK even if their actions were legal in the country they visited.
In some countries, possessing indecent images of children is not illegal, or the age of consent is lower than 16.
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