Australian federal police viewed rules governing parliamentary privilege as an “afterthought” in their haste to seize leaked communications about Peter Dutton’s grant of visas to au pairs, a Senate inquiry has concluded.

In a report tabled on Tuesday the Senate privileges committee concluded the police had a “genuine” inadequate understanding of the rules but it declined to make a finding that they acted in contempt of parliament.

The committee recommended that rules be clarified to specify that police must take into account likely privilege claims to prevent protected documents being read before a privilege claim was made.

On 11 October, police executed a warrant to search the office of an Australian Border Force employee, investigating leaks about Dutton’s ministerial intervention in the case of two foreign au pairs.

Documents seized include emails to and from Labor senator Louise Pratt’s private account from 28 August to 6 September, relating to a Senate inquiry into Dutton’s handling of the matters.

Labor immediately claimed parliamentary privilege over the documents, triggering a process that requires the documents be locked and not examined by police until the committee could consider the claim.

The committee concluded that on a “narrow reading”, the guidelines on how to treat privileged material are triggered only when a claim is made.

The committee concluded that there was an “ambiguity in the language” of the rules and a “genuine inadequacy in the AFP’s understanding of matters of parliamentary privilege”.

The committee said it was concerned that the rule book on how to deal with privileged information “appears to be an afterthought in AFP investigations”.

“In taking this course, it fails to recognise and respect the work of the parliament.

“Without the protection of privilege the parliament cannot perform its work and any action to diminish privilege erodes its work.”

In 2018 the Senate passed a resolution noting that parliament has the right to consider privilege claims and declare material is protected regardless of whether law enforcement agencies use covert or “intrusive powers” to seize material under warrant.

That motion called on the attorney general to work with presiding officers to develop new rules to protect privileged material.