More than 1,600 men have so far been arrested in Operation Ore, the huge UK police investigation into child porn on the internet.

Of those, 46 were suspected of being directly involved in child abuse, the officer in charge of the inquiry has told BBC News.

Another four have committed suicide, Assistant Chief Constable Jim Gamble of the National Crime Squad said.

And direct action has been taken to protect 40 children.

Operation Ore

Began when details of credit cards used on a US-based site were passed to UK police 6,500 names being investigated 1,600 arrested so far 46 thought to have been actively abusing children Four committed suicide Full inquiry may take two years Direct action taken to protect 40 children

Operation Ore is the UK wing of an American inquiry into websites that supplied child porn in exchange for payment via credit card, through which the users were tracked down.

Police have previously complained they lack the resources to investigate all the names passed to them by the Unites States Postal Inspection Service (USPIS), a federal agency that investigates online paedophile activity.

As Mr Gamble issued the latest update, he took the opportunity to urge the authorities to consider ways of banning some paedophiles from using the internet - and of monitoring others online.

"I think there are opportunities to further tighten legislation in respect of how we intrusively maintain surveillance of the online activity of known paedophile offenders," he said.

Townshend arrest

Police said nearly all those judged to be a priority - those working with children or in the criminal justice system - had been arrested.

Those held include several high-profile figures, including police officers involved in the Soham murder investigation and rock star Pete Townshend.

He says as an anti-paedophile campaigner he was accessing the sites purely for research.

On Tuesday, a consultant surgeon arrested as part of the probe escaped a jail sentence after admitting downloading indecent pictures of children.

Vascular surgeon Christopher Lattimer, 39, of Acol in Kent, was put on the sex offenders register and given a community rehabilitation order for up to three years.

Long investigation

The UK investigation began after the US Postal Inspection Service collected the credit card details of users of an internet portal which carried the message "child porn click here".

The details of 6,500 British cards were passed on to UK police, who have been tracing the users.

Police have warned they could be overwhelmed with the numbers of suspects involved.

Mr Gamble said it would take two years before everyone on the list was fully investigated.