Children being used as informants must have an appropriate adult present in meetings with the authorities, revised official guidance says.

A revised code of practice for use of covert human intelligence sources (CHIS), published on Wednesday by the Home Office, states that a parent, guardian, personal contact or professional such as a social worker should be present at meetings between sources aged under 16 and the police, intelligences services or other public authorities.

The requirement did not feature in an earlier version of the code, published in 2014. Its inclusion follows intense scrutiny of the practice of using child spies, after peers discovered powers covering the practice in obscure secondary legislation.

“Public authorities must ensure that an appropriate adult is present at any meetings with a CHIS under 16 years of age,” the code states. “The appropriate adult should normally be the parent or guardian of the CHIS, unless they are unavailable or there are specific reasons for excluding them, such as their involvement in the matters being reported upon, or where the CHIS provides a clear reason for their unsuitability.

“In these circumstances another suitably qualified person should act as appropriate adult, eg someone who has personal links to the CHIS or who has professional qualifications that enable them to carry out the role (such as a social worker).”

The code retains a passage prohibiting the use of CHIS sources under 16 being used to give information on their parents or legal guardians.

The requirement for an appropriate adult to be present in meetings with CHIS juveniles was included in the Regulation of Investigatory Powers Act under an amendment in 2000. However, it was not included in the published code of practice until now.

This month parliament’s joint committee on human rights was asked to investigate the use of juvenile sources by the police and security services.

The committee’s clerk confirmed that the chair of the Lords secondary legislation scrutiny committee, Lord Trefgarne, had referred the issue to the committee and it would be considered “in due course”.

The committee is not due to meet again until September, but the Guardian understands it is likely to find time on its already full agenda to look at the issue.

David Davis, the former Brexit secretary, Diane Abbott, the shadow home secretary, and a number of human rights groups have criticised the practice of using juvenile covert sources.

Juvenile CHIS could be used in operations as mundane as trading standards investigations into retailers selling cigarettes to underage customers. But in a response to the Lords, the Home Office said authorities also used child spies in investigations into suspected terrorism, gang crime and child sexual exploitation.