The global system designed to track paedophiles is failing as nations refuse to share information following the Edward Snowden spying revelations, child protection experts have warned.

Suspicions of government “snooping” and potential privacy breaches have meant that countries have proved unwilling to hold and disseminate information on known and dangerous child abusers.

The main system to identify offenders – The Green Notice, run by Interpol – is out of date and border authorities are failing to act even when known offenders are travelling to their countries, according to Ernie Allen, a senior US child protection expert who has worked with parliaments in 100 countries on designing new laws.

Of some 20 countries that have sex offenders’ registers, only a handful – including Britain, Australia, Ireland and the US – have any system of restricting the foreign travel of convicted paedophiles.

Mr Allen said that senior politicians from undisclosed countries told him they were unwilling to set up registers, believing that the data should not be held, or expressed concern about a public backlash over the holding of private information in the wake of the National Security Agency controversy.

Files leaked by Mr Snowden, an NSA contractor, revealed large-scale global monitoring by US and British intelligence agencies. Senior police figures say that the disclosures have hampered anti-terrorist work and damaged diplomatic relations.

“The NSA controversy has changed the whole balance between proactive dissemination and individual privacy,” said Mr Allen. “Law enforcement needs to know who is proposing to travel and it needs to have the capability to share that information within networks.

“I support the strongest possible protection for individual privacy but I don’t think it’s absolute. We’re not suggesting profile data other than information regarding people who have been convicted of crimes. You lose some of your civil rights when convicted of crimes against a child.”

The continuing expansion of international tourism and the internet has opened up the possibilities for offending abroad, but law enforcement has failed to keep up, he said. The failure of countries to alert others about the movements of paedophiles, or act on information, has resulted in a series of scandals that have left children alone with known offenders.

A convicted child abuser, Ian Bower, was able to molest children in Cambodia for five years after he fled from Britain in 2006 in breach of his release conditions. He went to work in South-east Asia as an English teacher but even after his arrest for the alleged abuse of children, British authorities failed to seek his extradition. He was finally jailed five years later in Cambodia.

The US has led the way in notifying countries of travelling paedophiles, with more than 100 notified about some 1,700 people convicted of child sex crimes, but it was not clear if countries acted on the information.

Mr Allen is part of an eight-strong team headed by Dr Maalla M’jid, the former UN special rapporteur, working on a new report on the sale of children, child prostitution and child pornography due out in 2016.