Staff at Canberra's Parliament House are preparing to walk off the job while the extraordinarily slow Federal public sector wage negotiations continue.

Department of Parliamentary Services staff have been waiting in vain for over a year for their bosses to make them a wage offer.

Now, the bureaucrats whose work is vital for the activities of federal politicians say they will disrupt Parliamentary Library, visitor, and research activities if there is no breakthrough soon.

The industrial action could include disruption to internal and external communications and uniform bans.

Union members are also considering reading prepared message to visitors and callers to the house, telling them about the pay dispute.

Meanwhile, public servants at the Attorney-General's Department have emphatically rejected the latest offer of a 1.5 per cent pay deal.

Departmental boss Chris Moraitis has conceded that the pay and conditions on offer fell short of the expectations of the 1750 public servants he oversees.

Community and Public Sector Union national secretary Nadine Flood said the result at the Attorney-General's Department showed union members were standing firm against the government's attempts to undercut their rights.

“Despite minister Abetz's recent spin, public sector workers are continuing to reject the Abbott government's unfair bargaining policy and will fight to protect their rights, conditions and take home pay," Ms Flood told Fairfax media reporters.

“It is disappointing to see minister Abetz try to cast aspersions on public servants by suggesting those who vote for such offers are 'economically literate' and implying that others are not.

“This is not the language of someone who respects the work and capacity of public sector workers nor their workplace rights and conditions.”

In a small breakthrough for the Government’s side of the negotiations, staff at the Australian Transport Safety Bureau have accepted a pay deal that is expected to see their wages rise slower than inflation.

Fifty-five per cent of the union members on staff voted to accept the deal.

The bureau's head of corporate services, Colin McNamara, said they were only giving up limited conditions, including a cut to personal leave from 25 to 18 days a year.

“This was partially offset by the introduction of three days compassionate/bereavement leave,” Mr McNamara told reporters.

“I believe the result [55 per cent in favour] reflects a general acceptance this is the best offer the agency can provide when taking into account our constrained financial position, the broader economic climate and what is transpiring across the public service.”