Unions fighting the decision of An Post to close its SDS parcel and courier service are to seek the intervention of the National Implementation Body (NIB).
They claim the decision to shut SDS without engaging with unions is a "most serious breach" of the Sustaining Progress partnership agreement.
This deal commits the Government to "active engagement" with the social partners on the future of commercial semi-State companies.
The commitment, initially given last year in a letter from the Taoiseach, Mr Ahern, to the Irish Congress of Trade Unions (ICTU), was restated in the national pay deal negotiated in June.
Union leaders say the "unilateral" decision by An Post last week to close the SDS service, with the loss of at least 270 jobs, contravenes this commitment.
Alleged breaches of Sustaining Progress can be investigated by the NIB, which is made up of high-level union, employer and Government representatives.
The decision to seek the involvement of the NIB was announced yesterday by the Communications Workers' Union (CWU) following a meeting between unions and the Minister for Communications, Mr Dermot Ahern.
Mr Peter Bunting, of the ICTU, who led the union delegation, said the exchanges with Mr Ahern were "robust".
It is understood Mr Ahern does not wish to intervene directly in the row as he believes commercial decisions about its future are a matter for An Post.
However, Mr Bunting said the ICTU had an agreement with the Government that any proposed changes in the semi-State sector would be the subject of "meaningful engagement" with unions, and this had not happened on this occasion.
Mr Ahern was a representative of the Government, "and we expect him to police that agreement", he said.
The general secretary of the CWU, Mr Steve Fitzpatrick, said the union would formally ask the ICTU to have the matter referred to the NIB.
The Government, he said, should not "stand idly by while management at An Post ride roughshod over the partnership agreement when the ink on that agreement is barely dry.
"In this regard, we have asked the Minister to call in An Post management, and subject their decision-making process on SDS to the rests required under Sustaining Progress."
A spokesman for the Minister said Mr Ahern had met the unions, and had agreed to meet them again next month. There had been a "frank discussion".
The company says it took the decision to close SDS, which has lost €20 million over the past two years, only after consideration of all other options.
It will be seeking 270 voluntary redundancies among the 450 staff at SDS, with the remainder transferring to other positions within An Post. The CWU claims that up to 400 additional staff could also be affected by the closure, but this is denied by the company.
