Hundreds of convicted sex offenders have gone missing across the UK, police have revealed, including 16 across Norfolk, Suffolk and Cambridgeshire.

New figures have shown 396 registered sex offenders are wanted because their whereabouts are unknown, including some who have been missing for more than a decade.

Cambridgeshire Police said 10 registered sex offenders were wanted because their whereabouts were unknown. They had been missing for between two and eight years.

Suffolk Constabulary said five registered sex offenders were classed as 'wanted' but did not reveal the length of time they had been missing.

Norfolk Constabulary said one registered sex offender had been missing since August.

One convicted sex offender in Gloucestershire has been missing since the year 2000, another in Northumbria disappeared in May 2002, while Humberside Police said the whereabouts of one registered sex offender had been unknown since September 2004.

Registered sex offenders - including rapists and paedophiles - are required to inform police and probation officers of their addresses and are supposed to be monitored by officials working under multi-agency public protection arrangements (MAPPA).

But in freedom of information responses to the Press Association, 39 forces revealed there were missing registered sex offenders in their areas in February or early March.

They stressed the figures could change as arrests are made or new cases come to light.

Every force to respond to the Press Association refused to name those missing over concerns of vigilante attacks or because the information was exempt under data protection laws.

The Metropolitan Police, the UK's largest force, said 167 registered sex offenders were wanted in London alone, including one offender who had been missing for 14 years.

A Scotland Yard spokeswoman said London's 'diverse multicultural population' meant a large percentage of sex offenders were 'either known or believed to be living abroad, having returned to their country of origin'.

West Midlands Police said 39 registered sex offenders were missing, including one since 2006 and nine between 2010 and 2012.

Greater Manchester Police said 25 registered sex offenders were missing, including one who disappeared in September 2005 and three others who went missing in 2006.

Essex and Sussex Police each said 11 registered sex offenders were missing in their force areas, while Cambridgeshire Police said 10 registered sex offenders were wanted because their whereabouts were unknown.

Sara Payne, whose daughter Sarah was abducted and killed in 2000 by convicted paedophile Roy Whiting, said: 'It's completely unacceptable that any registered sex offenders have disappeared from authority management, putting the public at risk.

'It's time to take some serious proactive action to bring them back under the police radar.'

The NSPCC described the figures as 'alarming' and said its own research had found there was just one police staff member responsible for every 50 registered sex offenders.

Jon Brown, the charity's lead for tackling sexual abuse, said: 'About half of those on the register are offenders who have raped or sexually assaulted children, or committed online child abuse image offences, however most just receive one police visit a year after they have been released from prison and a period of supervision.

'The monitoring of registered sex offenders in communities needs urgent attention by the Government to ensure it is fit for purpose.'

The NSPCC said there were around 900 police officers and non-uniformed staff responsible for managing more than 46,000 registered sex offenders.

'It seems this area is currently chronically under resourced and the number of dangerous individuals on the register is increasing yearly,' Mr Brown added.

Claude Knights, chief executive of the charity Kidscape, which aims to protect children from abuse, said: 'I think it is surprising there are almost 400 registered sex offenders who are unaccounted for in the UK because we have systems which are supposed to prevent that.

'We know that sex offenders are at their most volatile and dangerous when they are living in chaotic and unsettled circumstances.

'Registered sex offenders who are of no fixed abode are very difficult to assess and monitor, and most importantly are not complying with notification requirements.

'The safety of our communities depends on predators being on the appropriate radars. We have a duty of care to potential victims.'

A Home Office spokeswoman said: 'The UK has some of the toughest powers in the world to deal with sex offenders and we are committed to ensuring the system is as robust as possible.

'It is for the police to manage offenders in their area, but we work closely with forces to ensure legislation is effective and that officers have all the tools they need.'