Officers then secured a sexual harm prevention order through the courts, which included a condition that he must submit to a polygraph test when requested by police.

If he refuses it will be a breach of the order and he will be arrested, interviewed and could face the courts.

Essex Police now plans to extend the scheme to test previous offenders.

Detective Chief Inspector Jim Sandford said: "We use the polygraph test to get information about whether or not a sex offender is reoffending, so that we can assess the risk they pose to the public and ensure they are complying with sexual harm prevention orders imposed by the courts.

"We can't force people to take part unless it forms part of a court order and the results of a polygraph test can't be used as evidence in court.

"But the benefits are that it shows they are willing to engage and co-operate with the authorities, and it can prevent us relying on more intrusive methods of monitoring."