More than half the federal government’s agencies and departments have failed to put enterprise bargaining offers on the table and the hard line on wages and conditions mandated by the Coalition is emerging as the key reason for the delay.

Departmental bosses must secure the sign-off of the Australian Public Service Commission and at least two cabinet ministers before offers can be put to workforces.

But refusals of proposals for “productivity gains” are emerging as a key cause for the delay in getting the bargaining process started. There are 117 agreements covering 160,000 public servants up for renewal.

Both the commission and the government are refusing to talk publicly about their dealings with agencies.

It is understood several large agencies are embroiled in protracted negotiations with the commission, the authority enforcing the government’s edict that any wage increase offered must be offset by cuts to conditions.

In some instances, the commission is demanding departments hand over years of detailed wage data to allow the numbers to be crunched as proposed pay offers to ensure they meet “productivity tests” and are “cost assured”.

The Department of Foreign Affairs and Trade is the latest outfit to admit to its public servants that it was having trouble selling productivity proposals to the APSC and Public Service Minister Eric Abetz.

Senior DFAT executive Luke Williams told the department’s 4000 workers last week that Foreign Affairs Minister Julie Bishop and other “agency ministers” had signed off on a package that will include a pay rise.

But Mr Williams conceded that “initiatives and offsets” – productivity trade-offs that would allow the offer to proceed - had yet to be approved by the commission.

The senior public servant admitted that putting the numbers together had been a “challenge”.

“It will be up to the Public Service Commissioner … to consider the validity and dollar value of the initiatives and offsets, and what they could deliver in terms of a proposed remuneration increase,” Mr Williams wrote.

“Finalising the costings that underpin those initiatives and offsets is the challenge for us.”

Mr Williams said DFAT’s problems were being experienced across the Australian Public Service.

“Other agencies are just as focused on the costings issue, which explains why few agencies have thus far submitted a pay offer to their employees,” the DFAT executive wrote.

The Defence Department, which is still conducting an internal hunt for whoever leaked its bargaining position to the media before staff were consulted, told its workers it was worried about the below-inflation offer being knocked back.

“Feedback received is that packages that do not meet the productivity tests and are not cost assured will simply be rejected and more work required, further delaying the process,” deputy secretary Rebecca Skinner told her staff last week.

The Department of Human Services is the only public service agency to put a complete package to workers, a deal worth .8 per cent a year which is meeting fierce opposition among its 30,000 staff.

The Taxation Office, which is also understood to be battling to sell its productivity plans to the commission, declined to talk publicly about its problems.

“As part of our commitment to good faith bargaining we will not be publicly commenting on the negotiations during bargaining discussions,” a spokeswoman said.

The Public Service Commission said “it will not be releasing details concerning agency costing proposals”.

Senator Abetz’s office did not respond to inquiries before deadline on Monday.