The president of the Building and Allied Trades Union (BATU), Mr Mick McNally, has condemned the attack on the offices of the Plasterers' Union on Friday, when files were thrown into the street and set on fire.
The incident occurred shortly after two building workers were released from prison for defying a High Court order and for unofficially picketing a building site in Ballsbridge, Dublin.
The attack on the Plasterers' Union offices has highlighted divisions which exist between BATU and other building unions over sub-contracting. BATU wants all sub-contractors removed from sites while the other unions approve of a new agreement which seeks to regulate the practice.
The general secretary of the Plasterers' Union, Mr Niall Irwin, is also secretary of the Irish Congress of Trade Union's construction group of unions. His union rents its office from BATU.
The division between BATU and the unions in the ICTU construction group is now so deep that the group is expected to join with the employer body, the Construction Industry Federation, in a joint defence of the sub-contracting agreement against BATU in the High Court. BATU has sought an action to overturn the agreement, which arose from a 1995 Labour Court hearing.
"There are thousands of legitimate sub-contractors out there, including BATU members," Mr Irwin says. "We think the agreement is tailor-made for the industry and that it protects the workers."
Along with other building union leaders, Mr Irwin believes that BATU's opposition to sub-contracting is impractical.
The new agreement with the CIF recognises that a problem exists and commits the federation to ensuring that its members comply with its provisions. These include employment of the appropriate grades of construction worker for specific tasks; compliance with the relevant tax and social welfare legislation; accepting responsibility for health and safety requirements and payment of employer liability insurance.
While BATU has spearheaded the battle against sub-contracting within the official trade union movement, the Building Workers Against the Black Economy (BWABE) has done so through unofficial action. It draws members from all unions but its core group is made up of bricklayers from BATU. The attack on the Plasterers' Union offices, however, is leading to some members of both BATU and BWABE reviewing their tactics.
Mr McNally, who is not a member of BWABE, said he intended apologising to the Plasterers' Union on behalf of BATU for the attack. He also confirmed that the matter would be discussed at the next meeting of BATU's national executive.