Ministry of Justice staff at courts, tribunals and other ministry worksites throughout the country have gone on strike for 23 hours.
The workers, members of the Public Service Association, walked off the job at 11am on Monday and will not return to work until 10am Tuesday.
Their action came as part of a long-standing pay dispute.
"We're extremely disappointed the ministry has not been prepared to resume formal negotiations on a sound basis, given the fact the Employment Court has ruled that negotiations are not over and should resume," PSA national secretary Richard Wagstaff says.
On Thursday Chief Employment Court Judge Graham Colgan ruled that "at this stage the collective bargaining has not ended".
He says it is important that the parties now get back into bargaining.
The row has been brewing since May last year and the PSA's 1700 ministry employees began taking industrial action in October.
Wagstaff says members across the country have voted overwhelmingly to escalate the industrial action in support of a fair settlement.
The action is closing courts, forcing trials and hearings to be adjourned, backing up cases and disrupting other Ministry of Justice work around the country.
"Ministry of Justice staff receive are paid on average 6.9% less than workers in the rest of the public service," Wagstaff says.
"They'll continue to strike and take other action until the ministry agrees to sit down and negotiate a fair pay settlement that all parties can live with."
