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.
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.
South Yorkshire Police said 10 sex offenders were wanted because their whereabouts were unknown but refused to say how long they had been missing.
North Yorkshire Police said the whereabouts of two registered sex offenders were unknown - one who has been missing since 2008 and another since late 2014.
West Yorkshire Police said it needed more time to respond to a request for information.
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, 38 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.
In a statement through campaign group The Phoenix Post, 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 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.
The Police Service of Northern Ireland (PSNI) said three sex offenders were “currently wanted” but refused to say when the offenders went missing.
The force said it refused to disclose the names of those missing as the information may be “valuable” for “criminal/ terrorist/ vigilante groups who may attempt an attack on them and/ or their families”.
Police Scotland said none of the 4,775 registered sex offenders in the country was missing as of February 16.
Claude Knights, chief executive of the charity Kidscape, which aims to protect children from harm and abuse, said: “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.”