Police forces across the UK have lost track of the whereabouts of 322 convicted sex offenders, a newspaper has reported.
John Reid's department is under fire again
Using the Freedom of Information Act, the News of the World asked all 50 forces in England and Wales how many sex offenders are missing.
They are required to inform police and probation officers of their addresses.
The Home Office said the sex offenders' register was a "powerful operational tool" which had a 97% compliance rate.
The Metropolitan Police confirmed 88 offenders from London were missing.
But a spokeswoman refused to say how long their whereabouts had been unknown or give any details of their crimes.
She said the figure of 88 was low compared with the total number of registered sex offenders in the Metropolitan force area, but refused to say what that total was.
She said police were taking "pro-active" steps to try to trace the missing offenders.
The News of the World investigation also revealed West Midlands Police had lost 25 sex offenders and Greater Manchester 18.
Michelle Elliott, founder and director of the child protection charity Kidscape, told BBC News she was "shocked and annoyed" at the investigation's findings.
"These people are out in the community and they are going to commit more crimes and more children and more adults are going to be abused," she said.
She said the figures for sex offenders who re-offend were "really quite high".
"It's the ones who are trying to slip through the net that you have to worry the most about and these 300 are trying to slip through the net," she added.
Released sex offenders are supposed to be monitored by officials working under Multi-Agency Public Protection Arrangements (MAPPA).
But according to the News of the World, registered sex offenders - including rapists and paedophiles - have used a loophole in the system allowing them to register vague addresses in order to disappear.
Last year, one paedophile who breached register conditions was allowed to give his address as "woods" after moving from "a tent near Guildford leisure centre", the paper claimed.
LATEST HOME OFFICE PRESSURES
27 January...The News of the World claims 322 convicted sex offenders are missing across the UK
26 January....Home Secretary John Reid denies telling judges to give softer sentences to ease prison overcrowding
26 January....England and Wales Youth Justice Board head Rod Morgan quits over youth prisons' overcrowding
25 January....Risk of being a victim of crime in England and Wales rises for the first time since 1995, figures suggest
21 January....Proposals reveal the Home Office may be split in two to cover justice and security
14 January Senior civil servant suspended over failure to update police records of Britons convicted abroad
Shadow Home Secretary David Davis told the News of the World: "Yet again we see a serious failure of government criminal justice databases to do their job."
According to the newspaper, Cambridgeshire, Cheshire, Durham and Norfolk Police said they had no missing sex offenders in their areas.
Two police forces in Wales - Dyfed Powys and Gwent - did not provide a figure, it reported.
All the police forces refused to give details about the sex offenders or how long they had been missing.
The Home Office said the day-to-day management of the sex offenders' register was "rightly a matter for the police and probation services".
"Where an offender appears in breach of their notification requirements the police will update the police national computer and the sex offenders register to ensure that they are traced and dealt with appropriately," it said.
"The sex offenders register is a powerful operational tool for managing sex offenders in the community, with a compliance rate of 97% for those subject to its requirements."
"In the UK we have one of the most advanced systems in the world for monitoring and managing dangerous offenders."
The story will heap more pressure on Home Secretary John Reid, who is already under fire because his department failed to record the details of thousands of British criminals convicted abroad and also failed to enforce travel bans on 147 drug traffickers.
The minister was also criticised for writing to judges asking them to jail only the most dangerous and persistent offenders, to ease prison overcrowding, but Mr Reid said he was merely re-stating existing guidelines.