A row has erupted over the outsourcing of lighting, park and street sweeping services at the country's largest local authority.
A union has claimed that Dublin City Council has drafted in dozens of contracted workers to carry out key services, in addition to its own directly employed staff.
Although the council has not sacked or redeployed its own employees, there are fears the move could be the first step towards gradually replacing them with cheaper labour.
The dispute is a test case for the Croke Park agreement's provisions on the outsourcing of state services.
According to the deal, the public service is committed to the "use of direct labour to the greatest extent possible".
But it also says this should be "consistent with the efficient and effective delivery of public services", which is likely to be interpreted differently by management and unions.
IMPACT said it had evidence that around eight contracted workers were being used in street cleaning services in the city centre.
It also claimed private companies were being used in waste management services in Ballymun and Finglas, as well as more than four contract firms employing over 20 workers in lighting and park services.
The union also suspects that eight workers were taken on under an initiative between Dublin City Council and the business community, called BIDS, to clean the city centre.
It has referred the dispute to the Labour Relations Commission after claiming the move breaches the Croke Park deal because there was no consultation with staff representatives.
IMPACT official Johnny Fox said the union wanted clarity on the issue. "When the skills are not in-house, like when there are major road works, it is completely different and we wouldn't be opposed," he said. "But these staff are not needed and our members are well capable of these duties."
Dublin City Council refused to comment when asked if they had taken contractors on but insisted it was not in breach of the agreement.