The final sitting week of federal Parliament before the long winter break is set to be hit by public servants working in Canberra going out on strike in their masses.

Thousands of members of the Community and Public Sector Union are set to muster on Tuesday at the National Convention Centre as part of an authorised mass walkout in the national capital over deadlocked enterprise bargaining talks.

Large parts of federal agencies across the Australian Public Service are expected to be buffeted by the authorised stoppage in the National Capital, which the CPSU is pushing as a vital fight for the retention of key rights, entitlements and conditions — and not allowing the government to mete out what in some cases add up to effective cuts in take-home pay.

The Abbott government and the Australian Public Service Commission have so far shown almost no tangible inclination to compromise with the union over the enterprise bargaining dispute, a scenario that makes it increasingly likely that a bid for a third round of far more disruptive action by angry public servants is now on the cards.

With Parliament in session, the Tuesday mass walkout is certain to garner high profile publicity for a second week as it hits the very seat of Australian government and the federal press gallery.

“Already, across the nation, thousands of public sector workers have walked out on strike and gathered together to protest the Abbott Government’s attack on their rights, conditions and pay,” CPSU National Secretary Nadine Flood said.

“Now it’s time to bring their message to the nation’s capital – public sector workers will fight to protect their rights, conditions and pay from this unprecedented assault by the Abbott Government.”

Although most of the actions by the CPSU have to date been largely symbolic or tactical, the ultimate threat of far more targeted action aimed at disrupting or causing pain for the government — rather than hitting public-facing services — remains a live and potent option over coming months in an effort to break the year-long stalemate.

Meanwhile, government agencies with large numbers of customer have preparations well in hand to try and minimise disruption.

The Department of Human Services was on Monday reassuring customers that their money won’t be held up, but was also suggesting non-urgent calls to its agencies be put off until the action had passed, or use online channels.

“I want to assure our customers their payments will not be affected by this industrial action, as many are automatically generated and reporting requirements for payments such as Newstart Allowance can already be done online,” said General Manager Hank Jongen said.

“While we have robust contingency arrangements to minimise disruptions in circumstances like these, customers should keep in mind that we may have reduced numbers of staff to assist them during this period.

Human Services remains a key battleground in the APS bargaining dispute where many unionised staff remain angry over low-ball pay offers that have been hamstrung by the government’s strict bargaining policy in terms of reaching a compromise.

Even so, Human Services on Monday used the industrial action to indicate that it had not yet given up hope in its search for a compromise, despite previous offers having been overwhelmingly.

Another official bid for a compromise is expected in weeks, according to Human Services’ senior management.

“Since tabling our second pay offer in February we have not been sitting idle,” Mr Jongen said.

“We have been reviewing staff feedback to look at where we may be able to make further changes to the offer that is currently on the table, and have actively been exploring every option we can, within the Government’s bargaining policy, to give our staff an affordable pay offer.

“In fact, this work has resulted in a revised pay offer, which is currently going through the necessary government approvals and we expect to be able to table a further pay offer in July for staff to consider,” Mr Jongen said.

However Labor’s Shadow Minister for Human Services, Senator Doug Cameron, said Human Services staff had been provoked into striking after trying to negotiate a new enterprise agreement for nearly 18 months “in the face of the Abbott Government’s attacks on long established working conditions under the guise of ‘productivity improvements’.”

“It is now a month since DHS sent a secret proposal for a revised offer to staff to the Australian Public Service Commission for its approval before it can be put to staff,” Senator Cameron said, adding it was “well beyond time” Human Service Minister Marise Payne intervened “to have common sense restored to the bargaining process.”

The realpolitik of the negotiation is that the government is likely to have to cede some ground in terms of widening its present strict definition of productivity under the bargaining policy so that it can factor-in more than just straight labour cost savings.

Part of the government’s wider characterisation of public servants having it easy have also been dealt a blow after a blistering Audit Office report on Centrelink’s call centres revealed the agency was, by its own estimate, 1000 staff and $100 million short of the resources needed to bring call waiting times down to five minutes.

The same Audit found that more than 25 per cent of calls to Centrelink hit an engaged signal and never even made it through into its choked call centre system.

“The department has estimated that to reduce the KPI to an average speed of answer of 5 minutes, it would need an additional 1000 staff at a cost of over $100 million each and every year.”

But there is less trepidation over the industrial at the Australian Taxation Office.

“The ATO has contingency plans in place to actively manage any industrial action in order to minimise any disruption to providing key services,” an ATP spokesperson said.

“All ATO sites and facilities will remain open for normal operating hours tomorrow and we expect there will be minimal impact for the community.”

However politicians and their staffers fearing they might get stranded for the weekend in Canberra can breathe easier. The CPSU on Monday scotched a rumour that flights out of Canberra could be hit by strikes, saying it had no knowledge of any such action.

On Monday the CPSU rumour among some political staff in the corridors of the Big House that some Qantas flights departing Canberra on Thursday and Friday could be affected by industrial action to leave departing politicians stranded.