People using the court system will be handed an open letter making the case for staff who have gone without a pay rise for four years and overwhelmingly rejected their employers' last offer with a 90 per cent 'no' vote in June.

"We work for the courts because we want to help you and make a valuable contribution to our communities. This is getting harder every day," the letter said.

It said delays in resolving court matters were causing problems and blamed a lack of investment in front line staff.

"Workloads have increased but staffing has not. A four-year pay freeze and cost of living increases mean our wages have gone backwards in real terms," the letter said.

"We deserve a sensible agreement that values and respects our contribution."

A Courts spokeswoman said it was in bargaining meetings with staff and was hopeful it would achieve a "suitable outcome."

Staff are negotiating a single agreement after the Federal Court of Australia's merger of administration with the Family Court and Federal Circuit Court in 2016.

The Federal Court's public servants said no in June to a proposal offering them half the wage rises being paid to their counterparts in other departments and agencies, a result Community and Public Sector Union Secretary Melissa Donnelly described as a disaster for Courts bosses.

The courts staff were asked to accept a new deal that offered an average pay rise of 1 per cent for each of the proposed agreement's three years, cuts to conditions and entitlements and, for some, a longer working week.

Ms Donnelly said that Courts was continuing to push an "insulting" pay offer despite the rejection.

"Our members know too well how frustrating the courts can be to deal with, particularly the long delays and complexity of the system. Without quality clerical and support staff the situation would be even worse. That's why the open letter is urging the public to speak up on their behalf," she said.

"Courts staff have been reluctant to take industrial action and are loath to do anything that would inconvenience people by putting hearing dates in jeopardy. But their patience is running thin and time is running out for management to start treating them justly."

The landslide rejection, from a voter turnout of 81 per cent in the 1187-strong workforce, came after deals paying 2 per cent were accepted at the Defence Department, the Australian Taxation Office, the Agriculture Department, the CSIRO and the Department of the Prime Minister and Cabinet.

A long-running dispute at the Department of Human Services ended last month with 70 per cent voting in favour of a new agreement.