A major sex crime crackdown has led to the arrest of 660 suspected paedophiles across Britain, the National Crime Agency (NCA) has said.

The six-month operation targeted internet users who access child abuse images but has already led to charges for serious sexual assault.

And every constabulary in the country was involved, including Hampshire.

But Hampshire Constabulary are currently refusing to reveal details of how many have been arrested and charged.

Among the several hundred people arrested across England, Wales, Scotland and Northern Ireland are workers who had access to children through their jobs and had no previous contact with police.

The massive investigation, involving 45 police forces, led to hundreds of children being ''safeguarded'', the NCA said.

It stressed that none of those arrested is a serving or former MP or member of the Government.

The NCA said suspects include doctors, teachers, Scout leaders, care workers and former police officers. In total, only 39 registered sex offenders are among those arrested.

Officers have searched 833 properties and examined 9,172 computers, phones and hard drives.

The NCA said it built up ''intelligence packages'' on suspects and sent them to police forces across Britain.

NCA deputy director general Phil Gormley said the crackdown, the biggest ever operation of its kind, involved alleged paedophiles who used the so-called ''dark web'' as well as traditional internet access.

The ''dark web'' is internet content that is not listed by normal search engines. Users will often use payment methods such as virtual currencies to help avoid detection.

The 431 children who were safeguarded were in the ''care, custody or control'' of the suspects, and included 127 who were deemed to be at immediate risk of harm.

Mr Gormley said he was ''profoundly disappointed'' that so many suspects had been arrested over this type of crime, and said a harder look needs to be taken at the high numbers of people accessing child abuse images.

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

Claire Lilley, head of online safety at the NSPCC, said: ''This is an important two-pronged operation which has rescued children from abuse and also identified many previously unknown sex offenders. Direct action like this sends a strong message to those who subject children to harrowing sexual assaults that they can and will be traced and prosecuted.

''But law enforcement agencies alone cannot deal with the vast problem of illegal images which continue to flood the market. Industry has to find inventive ways of blocking the flow of such horrendous pictures which are only produced through the suffering of defenceless children - many of who are not even old enough to go to school.

''So while this operation must be rightly applauded we should view it as yet another warning sign that far more needs to be done if we are to stem the sordid trade in these images, which are often used by those who go on to abuse children.''

Mr Gormley said sex offenders should realise that they cannot avoid detection while using the internet, even the dark web.

''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,'' he said.

In previous cases, officers have used undercover tactics, including posing as potential victims to lull sex offenders into showing their true colours.

The NCA deputy boss said: ''As our understanding increases of the scale and the nature of this type of offending enabled by the internet, there is a challenge. There is a challenge for law enforcement, there is a challenge for policy makers.

''Realistically, are we going to be able to arrest our way out of this problem? I doubt it. We are going to need to think about all sorts of measures around prevention, disruption, protection and pursuit.

''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.''