Workers from agencies including Human Services, the Tax Office, Immigration, Border Protection and Employment will walk off the job on September 15 amid concerns that staff are being "low-balled" by new enterprise agreements.

The union's national secretary, Nadine Flood, said the "unprecedented levels" of industrial action by tens of thousands of public sector workers in recent months would continue unless the Abbott government agreed to come to the table.

Ms Flood said public service minister Senator Eric Abetz has refused to meet with the CPSU since January 2014.

"Industrial action is not the preference for these workers or the CPSU. We are up for a sensible discussion but these workers feel like they have no choice," Ms Flood said.

"This dispute is about working mums and dads, ordinary people with families, bills and mortgages to pay who are struggling to get their employer to have a sensible discussion with them."

Ms Flood said that under the existing policy Border Protection workers will lose up to $8000 in stripped allowance, while working parents in Centrelink and Medicare will be forced to surrender work and family protections.

"We have seen working parents who are facing attacks on essential work and family protections at a time when other employers are increasing their offerings to attract and retain staff," she said.

"The government's bargaining position is more draconian that any major private sector employer in Australia. Perhaps it's time they rethought and considered a genuinely productive approach to their own workplace relations."

The lunchtime rally and half-day strike will be followed by further strikes and industrial action around Australia in coming weeks.

More than 17,000 public service jobs have been cut since the Abbott government took office.

Less than 2 per cent of public service workers have a new agreement in place.

"We have more than 160, 000 Commonwealth workers caught up in this bargaining mess," Ms Flood said.

"Very simply, we are prepared to meet with Senator Abetz anytime, anywhere to have a sensible discussion about resolving this dispute."

Meanwhile, Department of Human Services employees have until September 10 to vote on a new enterprise agreement.

The agreement includes an annual pay rise of 1.5 per cent over the next three years but removes casual loading for staff who work weekends, public holidays and outside normal business hours.

Australian Taxation Office bosses are also battling just to get a ballot up and running as unions take their grievances with the process to the industrial umpire.

Unions have applied to the Fair Work Commission for "bargaining orders" forcing Tax Office bosses to disclose more information before a vote on their wage offer is held.

Tens of thousands of CPSU members have already walked off the job at the Department of Human Services, the Bureau of Meteorology, the Department of Agriculture and the Australian Taxation Office this year.