UK citizens who commit sex offences abroad will face prosecution when they return to the UK - even if the act was legal in the country in which it took place.
The tough new legislation comes as part of the government's new Criminal Justice and Immigration Act 2008, which is due to become law on Monday.
"From July 14th, anyone who commits an offence against children abroad will face the prospect of prosecution for the same offence here even though it may not have been [an] offence in that country," home office minister Vernon Coaker explained.
The move follows government concerns about countries where the possession of indecent images of children is not an offence, or the age of consent is lower than 16.
The Home Office is selling the measures as an example of their initiative in tracking down sex offenders, but the origins of the legislation are more complex.
Legal experts contacted by politics.co.uk say the change in the law is part of a hasty effort to comply with the European Convention on the Protection of Children which was adopted by the Council of Europe at a conference in Spain last year.
Turkey, Sweden and several other countries have already ratified, but the UK is unable to do so until it updates its own legislation to allow prosecution for acts considered criminal in this country but legal in the country they were committed.
Interestingly, British citizens will now be open to prosecution regardless of the laws of the other country, but UK residents will not be.
Jim Gamble, chief executive of the Child Exploitation and Online Protection Centre, remained upbeat about the change in the law.
"This measure is a significant step forward and sends out a very clear and unequivocal message to offenders everywhere - and no matter whether they are in the UK or abroad - we will track you, we will bring you to account and you will face the consequences of your criminal actions," he said.