More than 1400 registered sex offenders are living in South Yorkshire – but police lost track of nine of them last year, according to figures.
Police officers know the whereabouts of nearly all of the 1434 criminals on the Sex Offender Register - including rapists and pedophiles - that are living in Sheffield, Doncaster, Rotherham and Barnsley - but admitted a small number have vanished without a trace.
Police have now lifted the lid on the sheer scale of work needed to monitor the whereabouts of sex fiends and revealed they now use lie detector tests to keep track of offenders.
Meanwhile, a sex abuse victim said it was 'disgusting' that so many sex offenders are living in our communities and the boss of a charity which helps victims called for harsher sentences.
The woman. who cannot be named for legal reasons, was abused by Doncaster man Timothy John Robinson-Perkins during the 1970s when she was just 10-years-old.
She branded her abuser's sentence of nine years as 'too lenient' as he is due to be back out in the community on licence after serving only half of the sentence behind bars.
She added: "I think it's disgusting. There are far too many, and far too many who get away with it. This has ruined my life. I've had depression for years."
Robinson-Perkins, aged 54, of Melrose Mews, Auckley, Doncaster, was found guilty of 10 sex offences following a trial at Sheffield Crown Court in December.
The figures were revealed using the Freedom of Information Act and are based on registers dating to December 2017 - which is when the request for information was made.
The data shows there were 447 sex offenders in Sheffield, 417 in Doncaster, 338 in Rotherham and 232 in Barnsley.
This includes predatory former Sheffield Steelers ice hockey player Thomas Squires.
The 26-year-old, formerly of Steven Crescent, Chapeltown, was jailed for five years and four months in March last year after admitting four counts of inciting sexual activity with a child and one count of sexual activity with a child.
Squires' offending related to five young girls aged between 13 and 15, none of whom can be named for legal reasons, and took place over a five year period between 2010 and 2015.
The FOI also revealed that last year's figures were higher than in the previous two years.
In December 2015 there were 1213 sex offenders in South Yorkshire, while in 2016 that figure rose to 1356. The statistics do not include those who are in prison.
Meera Kulkarni, chief executive of the Sheffield Rape and Sexual Abuse Centre, said sometimes sentencing decisions and parole arrangements 'do not reflect the gravity or impact of the offence.'
She added that for abuse survivors knowing that their attacker is back out in the community can lead to 'huge stress and anxiety'.
She added: "They may be reminded of their original abuse and their feelings related to that abuse for example fear, anxiety, depression and powerlessness can become more overwhelming."
However, the charity boss expressed sympathy for police as they are 'facing an ever growing Sex Offenders Register' with 'ever dwindling resources'.
She added: "Effective communication with victims when an offender’s release is being considered or imminent should be part of this transfer back out into the community."
South Yorkshire Police put the rise in figures down to more widespread reporting of sex crimes, including historic cases, and said it was also due to the use of more advanced technology enabling them to catch more offenders.
A spokeswoman for the force said: "South Yorkshire Police has a dedicated team of officers and staff who robustly manage sex offenders on a daily basis.
"This involves working closely with partner agencies including the Probation Service, carrying out unannounced visits and the use of polygraph testing on registered sex offenders where appropriate.
"In recent years, South Yorkshire Police has seen a dramatic increase in the reporting of sexual offences, both current and historic, due to a greater confidence among victims and technological advances to assist the identification of on line offences."
She added: "Policing techniques continue to become more advanced and robust which is leading to more charges and ultimately convictions.
"Offenders found guilty of serious offences who receive substantial prison sentences are placed on the register for life, so nationally the trend is for the number of people on the register to continue to grow."
Number of registered sex offenders living in the community
December 2015 – 1213 in South Yorkshire (individual towns and cities not available)
December 2016 – 1356 in South Yorkshire – Sheffield 456/Doncaster 380/Rotherham 319/Barnsley 201
December 2017 – 1434 in South Yorkshire – Sheffield 447/Doncaster 417/Rotherham 338/Barnsley 232.