The number of registered sex offenders in Suffolk has risen sharply in the last year and police admit five of them have gone missing.

Latest figures for 2011/12 show there were 584 people on the Sex Offenders' Register in the county – an increase of 45 from the previous year when there were 539 offenders and 2009/10 when 489 people were on it.

The continuing growth of the register as more people are placed on it each year is putting police under increasing pressure to supervise and has led to special constables being drafted in to help.

In a new report to a Suffolk Police and Crime Panel committee, Chief Superintendent David Skevington, head of protective services for Norfolk and Suffolk, outlined the problems facing his officers.

He said: 'As reported previously the level of registered sex offenders in both counties inevitably continues to rise. Measures are in place to manage the risks to this area of business.

'Initiatives such as training and deploying special constables to carry out joint visits alongside public protection officers are in place in both counties and beginning to work well. There will, however, remain pressure on resource levels in this area.'

It has emerged that the whereabouts of five of the registered sex offenders in the county is unknown, despite their obligations to notify authorities of any change of address.

Det Ch Supt Skevington added the force takes its role in managing sex offenders seriously.

He said: 'The management of risk in the community is provided under the Multi-Agency Public Protection Arrangements (MAPPA), which involves police, probation, social services and other partner agencies.

'The protection of the public remains our highest priority. Suffolk Constabulary has a dedicated team who monitor, risk assess and enforce the law applied to those people on the Sex Offenders' Register.

'The Sex Offenders' Register is a powerful tool but it is also about engagement of all agencies to actively manage sex offenders to reduce the risk they pose and increase public safety.'

Suffolk's Police and Crime Commissioner Tim Passmore said the number of registered sex offenders is too high and that is why special constables are being drafted in.

He said: 'We are on the case and we will get those responsible.

'We are pursuing the serious cases and have a very good record of prosecution for the very serious offences such as rape and sexual attacks.'