Three of the largest ISPs in the US have struck a legal deal to block child pornography sites, mirroring a voluntary agreement which already exists among the majority of UK ISPs.

Verizon, Sprint and Time Warner Cable have agreed with New York Attorney General Andrew Cuomo to block sites and Usenet newsgroups that are known to disseminate child pornography.

The ISPs had insisted that they were not responsible for content viewed by their subscribers. But they caved in when Cuomo threatened to charge them with fraud and deceptive business practices, according to The New York Times.

In the UK, 95 per cent of broadband connections are already covered by a voluntary blocking agreement between the largest ISPs and the government which was brokered in 2004.

"The UK has taken a collective approach to addressing this issue, and has had considerable success in ensuring that the sites on the Internet Watch Foundation list are blocked," a Home Office spokesman told vnunet.com.

The Home Office said that it is currently putting pressure on the remaining few ISPs to follow suit.

"We would like to restate the target given by ministers that all existing ISPs supplying the consumer market should implement blocking of child sexual abuse websites by taking the IWF list and preventing access to these sites by their customers," said the spokesman.

"As ever, we will continue to consider what further action or measures might be needed."

While the US deal has been largely welcomed by law enforcement agencies, it has been criticised in a report by the Financial Coalition Against Child Pornography formed by credit card companies and ISPs to cut off funding for these crimes.

Prior to the US deal customers paying for child pornography, and hence funding further perpetration of the crimes, were easily tracked by credit card payments.

The report reasons that the ban among ISPs will push child pornographers towards unregulated web payment companies that allow anonymous purchases.

Last month the UK Justice Ministry moved to ban the creation, possession and transmission of computer-generated images and non-photographic depicting child sexual abuse.