The Road Safety Authority is notifying candidates due to sit their driving tests next Wednesday afternoon that their tests will be rescheduled due to industrial action by the driver testers' union, IMPACT.
It is understood that around 400 tests due to be carried out by 100 testers nationwide will be affected.
The dispute centres on plans by the RSA to recruit a reserve panel of six testers to fill in when staff testers are ill or otherwise unavailable.
An RSA spokesperson said that in 2012, 12,000 test dates were disrupted due to the illness of testers.
Of those, 8,000 could not be dealt with through spare capacity, leading to inconvenience for candidates and lost revenue for the RSA.
The authority wants to recruit a reserve panel of six standby testers to plug gaps caused by illness at short notice.
However, IMPACT has criticised the outsourcing of the work, and accuses the RSA of breaching rules on consultation and negotiation.
It says that if the dispute is not resolved, further stoppages cannot be ruled out.
The testers rejected the latest Labour Court recommendation on the dispute on the basis that it did not provide adequately for negotiation with the union.
But, the testers' union IMPACT has criticised the outsourcing of the work, and accuses the RSA of breaching rules on consultation and negotiation.
IMPACT Assistant General Secretary Denis Rohan said the Labour Court had recommended the recruitment of a reserve body of qualified testers, to avert any possible backlog in test applications.
He claimed management had ignored the Labour Court recommended process and had instead moved to hire subcontractors instead of recruiting reserve staff.
He also alleged that management had since refused to talk to the union about the issue.
Mr Rohan acknowledged that a subsequent Labour Court recommendation in January had been rejected by driver testers, because it made no provision for talks on outsourcing arrangements.
IMPACT argues that the RSA outsourcing proposals could also breach the Authority's own safety standards, as it was not insisting that subcontractors hold the HETAC driver-tester qualification, which is a requirement for all RSA testers.
The union says the staff involved felt they had been forced into the action because management was refusing to deal with the issue.
However, IMPACT said it had decided on a relatively short stoppage to limit the inconvenience to clients.