Convicted paedophiles could be operating under cover of witness protection programs, the ACT Ombudsman says.

The Ombudsman's office has identified a loophole in the laws around the territory's sex offenders register that could allow convicted child sex offenders to escape registration and supervision if they are ''protected witnesses'' from interstate.

The office has urged police and justice authorities to establish better communication with their interstate colleagues so that predators cannot slip into the territory, protected from official registration by their home state's witness protection program.

Both the program, designed to protect witnesses against reprisals from violent criminals, and the child sex offenders register are subject to strict secrecy provisions and the Ombudsman's office is worried that not enough information is being shared.

''As noted in our previous reports to the minister, the ACT witness protection program may not be receiving sufficient information from witness protection programs in other jurisdictions regarding the movement of protected persons including protected registrable offenders entering the ACT,'' the Ombudsman's annual report reads.

''This implies that ACT Policing may not be informed of the movements of registrable offenders that are part of a witness protection program and are entering the ACT, and therefore may not place the offender on the register, as required under the act.''

The Ombudsman's office says it has urged police and ACT government justice authorities to open up dialogue with their interstate colleagues to close the loophole, and notes in its report that the process has already begun.

''This issue cannot be resolved by ACT Policing alone and requires the co-operation of the ACT Department of Justice and Community Safety and the witness protection programs in all other jurisdictions to establish communication channels regarding information about protected witnesses,'' the office wrote.

''We understand that the ACT Policing and the ACT Department of Justice and Community Safety are working with other jurisdictions to help address the issues.''