The Abbott government has picked a ''big industrial brawl'' with its ''ugly'' approach to the jobs of 160,000 federal public servants, according to the service's main union.

Another union is warning that serious workplace strife is inevitable with below-inflation pay rises predicted and big departments admitting they will not even be able to start talking for at least two months.

Public Service Minister Eric Abetz accused unions of endangering thousands of jobs with a pay claim of 12 per cent over three years.

The bureaucracy's biggest union, the CPSU, will gather more than 200 of its activists in Canberra on Thursday and launch its campaign against the government's policy position, which was released last week.

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The hardline policy offers no pay rises for departmental staffers unless their bosses can prove they have extracted ''productivity gains'', and there is pressure on public service chiefs to crack down on sick leave.

CPSU national secretary Nadine Flood says Senator Abetz is using the jobs of the 160,000 public servants in a broader political fight over the government's industrial relations agenda. ''They're trying to hide a serious attack on workers' rights and conditions behind 45 pages of dry technical language,'' Ms Flood said.

''Minister Abetz is using pay as a distraction to avoid talking about his attacks on workers' job security and conditions. They have effectively decided to use government bargaining as a political football rather than settle agreements and get on with it … they have chosen to make this part of a bigger political fight.''

Ms Flood's union will issue a call-to-arms this week to tens of thousands of public servants in the government's frontline departments.

''This policy asks a frontline Customs officer to accept cuts to jobs, an increasing work load, cuts to rights, cuts to conditions, cuts to real wages,'' Ms Flood said. ''It's not exactly fair and reasonable.

''We did not want a big industrial brawl over public service bargaining, we wanted to settle reasonable deals.

''What this policy does is it says the government wants a fight.''

Departments are telling unions that they will not be able to negotiate until they see in what shape next month's budget leaves their finances and then navigate the bureaucratic and political hurdles contained in the bargaining framework.

The Australian Service Union's tax office organiser Jeff Lapidos said it was ironic the government released its policy after the much-hyped ''bonfire of red tape''.

''They deliberately released the policy after the bonfire so they could tie up the departmental secretaries in red tape,'' Mr Lapidos said.

Professionals Australia official Dave Smith warned that industrial disputes were inevitable, with his members potentially going backward in their pay and conditions.

''They're stripping their agreements, not even having having pay agreements that keep pace with the cost of living, and then they don't expect that people are going to push back at that?'' Mr Smith said. ''We will certainly be supporting our members in talking whatever action in the Fair Work Act they have.''

In a statement supplied through his Canberra office on Wednesday, Senator Abetz accused the CPSU of being out of touch with its own membership.

''The CPSU's job-endangering 12 per cent wage claim is out of touch both with budget circumstances and their own constituency,'' the minister said in his statement.

''It will potentially cost another 10,000 jobs on top of the 14,500 cuts inherited from Labor. I think most public servants realise this.''