Four construction unions have queried the negotiating position of fellow union Unite at a recent Labour Court hearing on pay rates in the construction sector.
The move comes as a strike by crane drivers represented by Unite have shut down two key sites in Dublin
The dispute looks set to escalate next month as the union extends its ballot to all Construction Industry Federation firms.
The four unions' joint statement highlights the mounting tension and divergence in industrial strategy between them and Unite, which has been accused of poaching members from SIPTU, which traditionally represented crane drivers.
SIPTU has lodged a formal complaint against Unite with the Irish Congress of Trade Unions, and the outcome of that hearing is awaited.
SIPTU, the Building and Allied Trades' Union (BATU), the Electrical Engineering and Construction Union (TEEU), the Plasters Union of Ireland (OPATSI) and Unite are all members of the ICTU Construction Industry Committee.
However, SIPTU, BATU, the TEEU and OPATSI have issued a statement saying that it has come to their attention that building workers are being told that Unite was pushing for a 15% pay rise while the ICTU argued for a 10% rise at a Labour Court hearing last Monday.
They query the accuracy of this version of events.
They say that in 2015, all construction unions were pressing for a 7.5% pay rise to restore a previous 2011 pay cut, as well as a 2.5% pay rise over three years.
In total, that would amount to a 15% increase.
The four unions say that it was subsequently agreed unanimously by all unions - including Unite - to press for new minimum rates equivalent to a 10.2% pay rise above current agreed construction rates.
They say that the objective is to secure this increase now, and to get it enshrined in a legally binding Sectoral Employment Order, so that there would be no undercutting by non-union competitors.
Their reiterate that this strategy was agreed unanimously by all unions, including Unite, as the best way to make progress at this point in time, adding that Unite did not make any alternative proposal at Monday's Labour Court hearing on the SEO.
The Construction Industry Federation has described today's strike as irresponsible.
CIF Director General Tom Parlon noted that within the past six weeks, the CIF agreed a pay deal with SIPTU giving crane drivers two extra hours pay per day for "greasing time" - but that Unite is now seeking a further unaffordable claim.
He said construction companies had been caught in the crossfire of an inter-union dispute.
He noted that yesterday at the National Economic Dialogue, ICTU General Secretary Patricia King had made an impassioned plea for more housing - but that Unite, an ICTU member, had stopped activity on a key housing project.