There have been angry scenes outside the Labour Court where the Construction Industry Federation is making its case for a 10% pay cut for 190,000 building workers.
Around 15 protesting construction workers shouted abuse at CIF Director General Tom Parlon as he arrived to make his submissions.
Gardaí arrived at the Labour Court following a complaint that Mr Parlon was spat at as he attempted to enter the building.
SIPTU National Organiser Noel Dowling accused builders of making huge profits on the back of exploiting workers.
Both the CIF and the construction unions made their submissions to the Labour Court.
The CIF is arguing that due to the recession, up to 55,000 jobs could be at risk in the next five months if pay is not cut.
Unions reject that view and are seeking payment of a 3.5% wage increase now due under the national wage agreement.
They point out that the National Employment Rights Authority found that 62% of construction employers inspected last year had breached employment laws.
Wage rates in the construction sector are set by a legal mechanism called a Registered Employment Agreement.
The CIF was expected to tell the Labour Court that employers can no longer afford REA pay levels.
It says that with zero inflation and a recession, pay increases cannot be justified, especially since both the Government and IBEC have rejected the terms of that agreement since it was negotiated in September.
Elsewhere, SIPTU has called on construction workers to take part in a demonstration to be held in Dublin tomorrow in support of the Irish Congress of Trade Union's ten-point national recovery plan.
