Several hundred suspected paedophiles including doctors, teachers and former police officers have been arrested in the biggest ever UK crackdown on obscene images of children.

The unprecedented six-month operation headed by the National Crime Agency (NCA) saw 660 people held for downloading and sharing the sickening pictures, and has already led to charges for serious sexual assault.

Among them 10 men from across Suffolk and 14 from Essex have been arrested. There have been no details released yet of whether they were in positions of trust.

A Suffolk police spokesman said: “We can confirm Suffolk Constabulary received a number of referrals resulting in the arrest of ten individuals to date broken down as: a 26-year-old man from Needham Market, a 66-year-old man from Ipswich, a 58-year-old man from Ipswich, a 45-year-old man from Beccles, a 18-year-old man from Lowestoft, a 42-year-old man from Ipswich, a 44-year-old man from Sudbury, a 29-year-old man from Ipswich, a 31-year-old man from Ipswich and a 45-year-old man from Ipswich.

“All are currently on police bail. In total across Norfolk and Suffolk 347 computers and related equipment such as storage devices were seized along with 36 mobile phones.”

In Essex, police executed 31 search warrants in the county as part of Op Notarise.

A force spokesman said: “These investigations have subsequently resulted in 24 men being arrested on suspicion of the possession of indecent images of children. They all currently remain on police bail pending further enquiries. In total 20 children have been safeguarded due to the police activity in Essex.”

DI Danny Stoten, of Essex Police, said: “We have been working closely with the National Crime Agency to develop this intelligence and then execute search warrants and make arrests whenever possible. The information provided to us via Notarise has allowed us to pick up a range of suspects who had previously been operating under the radar.

“Offenders need to know that the internet is not a safe anonymous space for accessing indecent images. They leave a digital footprint and we will use all the means at our disposal to find it.

“If anyone has information relating to child sexual exploitation or suspicions that someone is using the internet to access indecent images I would urge them to contact the Essex Police On-line Investigation Team on 101.”

The breakdown of the search warrants executed in the policing districts include nine in Colchester, three in Tendring and five in Chelmsford.

Nationwide among those arrested included a doctor who had access to more than one million depraved pictures, was found to have met up with boys and kept sex aids and rope in the boot of his car.

Scout leaders and care workers were also among the huge number of people held across England, Wales, Scotland and Northern Ireland, and the vast majority had never before aroused suspicion.

The massive investigation, involving all 45 British police forces, led to 431 children who were in the “care, custody or control” of the suspects being “safeguarded”, including 127 who were identified as being at serious risk of harm.

Those arrested had used the internet or the so-called “dark web” – internet content that is not listed for access by normal search engines.

NCA deputy director general Phil Gormley said: “This operation has been about protecting children who are victims of, or might become victims of, sexual exploitation.

“Children are victimised not only when they are abused and the images first taken, but at every subsequent time that image is viewed by further offenders or distributed.”

Mr Gormley said he was “profoundly disappointed” that so many suspects had been arrested over this type of crime.

He said: “The alternative is not to look under the stone, and we cannot afford not to look under this stone.

“There are very significant volumes of people viewing this material in this country and abroad. We are going to need to understand as a society how we are going to confront this issue.

“We are not going to be able to arrest our way our of it. The numbers are significant, the volumes are huge.”

The NCA would not reveal the precise tactics it had used, but in previous child abuse cases officers have gone undercover and posed as potential victims to lull sex offenders into showing their true colours.

Chief Constable Simon Bailey, who is the national lead for child abuse investigations, said that police can track paedophiles online, even when using the dark web.

“Law enforcement now has the capability to see what people are doing,” he said. “Six hundred and sixty people have currently been arrested, there will be more arrests. There is a clear message to anybody using the internet to facilitate and to commit this type of crime that you are vulnerable.”

There were only 39 registered sex offenders among those arrested, with the majority able to avoid detection until now.

One of the suspects said he had been viewing images of child abuse for 30 years and had repeatedly travelled to south east Asia as a sex tourist.

When asked how hundreds of sex offenders had escaped detection until now, Mr Gormley said: “It’s a bit like a drugs problem. You need to look for it if you’re going to find it. People are unlikely to report this type of crime, you’re not going to have witnesses to it in the way that traditional crime types will.”

Two years ago the NCA estimated that 50,000 people in the UK were involved in sharing child abuse images online, and in the past 20 years the number of images available has soared from an estimated 10,000 to tens of millions.