UK ISPs have been urged to follow guidance issued by the Internet Watch Foundation, blocking subscribers from known child porn websites.
Some 95 per cent of home broadband connections in the UK are currently provided by ISPs complying with the policy.
However, five per cent of broadband users, mainly signed up to smaller broadband providers, are not blocked from such web addresses.
Home Office minister Alan Campbell said that the government fully supports the blocking of such sites: "In 2006 the government stated that they wished to see 100 per cent of consumer broadband connections covered by blocking, which includes images of child abuse, by the end of 2007.
"Currently in the UK, 95 per cent of consumer broadband connections are covered by blocking. The government is currently looking at ways to progress the final five per cent."