TThe government has "turned a blind eye" to Britons involved in illegal sex tourism abroad, a children's rights charity claimed as Gary Glitter, the disgraced former rock star, prepares for his release from a Vietnamese prison and deportation back to the UK.

According to End Child Prostitution, Child Pornography and the Trafficking of Children (ECPAT), which campaigns against the commercial sexual exploitation of children, many British sex offenders and paedophiles are living undetected in a "twilight zone" of international travel.

The charity says the UK Government is failing to prevent child sex tourism with the result that serious sexual offenders are "travelling from country to country and flagrantly avoiding the stringent sex offender mechanisms in the UK".

The claim is made as Paul Gadd, 64, otherwise known as Gary Glitter, is to be released from prison in Vietnam after serving a sentence for sex crimes against two girls aged 10 and 11.

The former glam rock star was jailed for three years in March 2006, but his sentence was reduced as part of an amnesty and he will be put on a plane back to the UK tomorrow. However, it is understood he will not be accompanied on the flight home, which could make a stopover in Bangkok in Thailand.

ECPAT is calling for stronger co-operation between foreign governments to deport and chaperone convicted paedophiles back to the UK so that they can be registered, tracked and, where necessary, have restrictions placed on their movements.

It is concerned that long-haul flights, such as those from Vietnam, do not always fly direct to the UK. The charity's report into the issue, published today, says: "To avoid offenders absconding on a stopover it is essential to have law enforcement or diplomatic chaperones from either country to escort the individual back to the UK."

If Gadd does arrive in the UK, he will be met by police at the airport and required to sign the sex offenders' register.

ECPAT says that while only five sex offenders have been prosecuted in the UK for child sexual abuse abroad since 1997, the US has prosecuted 65 and Australia 28. Between 2006 and 2008 at least 15 Britons were charged in Thailand for child sex abuse. Others - many of whom were teachers or volunteers in orphanages - have been prosecuted in countries including India, Ghana, Vietnam, Cambodia, and Albania.

The charity recommends a review of the use of Foreign Travel Orders (FTOs), which restrict the movements of high-risk sex offenders. It claims three FTOs have been issued to child sex offenders compared to more than 3000 to football hooligans.

New measures came into force last month allowing paedophiles who abuse children abroad to be prosecuted in Britain, even if their activities were legal in the country where they took place.