Angry public servants have lodged an industrial dispute over a controversial “dob in a mate” clause governing how staff in sensitive Canberra departments use social media.

The Community and Public Sector Union (CPSU) said on Wednesday it was launching a dispute with the Department of Prime Minister and Cabinet over the new regulations, which say there is an “expectation” that colleagues should report co-workers for posting critical comments on social media, even if they are done anonymously.

The policy applies to social media use both at work and outside workplace hours.

The union said the controversial clause was not included in the draft version of the policy but members expressed concerns about the dobbing issue after it appeared in later consultations.

Nadine Flood, national secretary of the CPSU, said: “We believe public sector workers should have the same rights as other Australians to engage in online debate, particularly when it’s in their own time and they don’t identify themselves as a government worker.

“This policy could mean that a public servant could be in breach of the rules if they attended a political rally and their picture is then shared on social media. That is not fair.”

The department said in a statement: “The department considers the social media policy is appropriate. It is an internal document for employees and is consistent with APSC guidelines.”

“The department will make no further comment.”

But Flood said that encouraging employees to dob in their colleagues “is a new and nasty feature and one that we think is unnecessary to police the use of social media”.