A child pornography crackdown which netted 200 suspected paedophiles in Sussex is just the tip of an iceberg, a senior detective warned today.

Sussex Police are reaching the end of a two-year investigation into an internet child porn network but more sick sites are expected to be uncovered.

Detective Chief Superintendent Graham Cox, head of Sussex CID, said: "It would be naive to think there are no more offenders to be identified."

Operation Chaucer, launched two years ago, was the force's response to an international crackdown codenamed Operation Ore which tracked thousands of suspects round the world.

Nationally, police say 100 children have been rescued from abuse or potential abuse as a result of inquiries triggered by tracking subscribers to internet porn sites.

One Sussex suspect has been separated from two children by social services as a precaution.

A total of 7,250 people were identified in England and Wales, officers were told at a seminar in Birmingham yesterday.

Of those, 3,500 were arrested, 4,100 addresses were searched, 1,670 people have since been charged with offences and 1,230 people convicted.

In May last year, The Who guitarist Pete Townshend apologised after being identified by Operation Ore as having accessed child porn on the internet.

The musician was cautioned and put on the sex offenders register but was not charged as he had not downloaded illegal images. He said he accessed the sites as part of research into paedophilia.

Operation Ore was launched in May 2002 following an investigation by the US Postal Inspection Service into Landslide Inc in Fort Worth, Texas.

This was a multi-million-dollar web site selling adult pornography and images of child abuse.

Backed by the FBI, the investigation revealed customers around the world.

The UK's National Crime Squad followed up leads in this country.

Sussex Police were given a list of local suspects and Mr Cox said yesterday their inquiries should be completed by June this year.

By the end of last year, almost 180 Sussex suspects had been arrested and Mr Cox said there had been a number of further arrests since.

Of those arrested to date, up to 80 have been charged or cautioned. Some cases are ongoing.

Many have been prosecuted and sent to prison, including a man who was a Sussex Police inspector at the time. Christopher Wratten was jailed for six months for downloading child porn.

Others have been cautioned and all those found guilty have been put on the sex offenders register. A number have been cleared or the charges against them have been dropped.

Mr Cox said the operation highlighted how the internet was making it easier for perverts to access material that they would otherwise have difficulty finding.

He said he would like to see action to rid the internet of such material.

He said: "Among those arrested in Sussex I am sure the experience has shocked them into never accessing such material again.

"But I daresay one or two have such a compulsion they will reoffend."