The territory government's deputy director-general of workforce, capacity and governance, Meredith Whitten, sent all staff an email on Monday stating that the government had approved staff participation in the Change the Rules rally on certain conditions.

The rally is part of a campaign by the Australian Council of Trade Unions, which is pushing for wage rises and improved job security across the country.

The tag line "change the government, change the rules" is about the federal Coalition government. Federal Labor has promised to reverse penalty-rate cuts if they win the election.

In the email, Ms Whitten said: "The ACT government recognises the importance of unions and the role they play in our society".

"The government actively supports the right for staff to collectively organise and to participate in campaigns such as these.

"All staff, contractors and temps are encouraged to attend the rally during their lunch break. You may also wish to take paid time off to attend the rally.

"Managers will be reminded that the government supports your participation and paid time off work will be approved unless there is genuine disruption to the public or to government operations."

However Ms Whitten went on to warn public servants that if they attended the rally, they did so as private citizens.

"It is important to ensure that participation in the rally does not give the impression that you are acting in an official capacity as an ACT public servant," she wrote.

It follows another email from Ms Whitten last year requiring ACT government executives to "actively encourage" their staff to join a union, including giving new starters membership forms.

Union officials or representatives also must be given the chance to recruit new members during work hours "provided that work is not unreasonably disrupted". They must also be invited to address new employees as an "integral" part of their inductions.

However an ACT government spokeswoman said they recognised that the decision to join a union remains at the discretion of the individuals.

"The purpose of the email was to inform staff of arrangements for the rally. This is not unusual practice," the spokeswoman said.

"Previous campaigns have been supported in similar terms. Workers are reminded to ensure ACT government operations are not disrupted, encouraged to use their lunch break to participate, and asked to be mindful that any participation is in a private capacity."

But Canberra Liberals' public sector management spokeswoman Candice Burch said the directive was "inappropriate".

“This type of blatant disrespect for the impartiality of public servants just goes to show how arrogant this Labor government has become," she said.

“I think ACT taxpayers are right to question the integrity of this practice and this misuse of public funds.”