The new national partnership agreement, which includes a 10 per cent pay rise for workers over 27 months, is expected to be formally ratified at a special delegate conference of the Irish Congress of Trade Unions (Ictu) in Dublin today.
An official result of a "card vote" is expected by lunchtime.
The conference, which brings together all the constituent unions of the Ictu in a vote to accept or reject the agreement, follows a series of ballots by some of the largest unions in recent weeks.
About 400 delegates representing 600,000 workers in the public and private sectors will take part in the vote.
Four of the largest unions - Siptu, Impact, TEEU and Amicus - have voted in favour of the agreement in ballots of their members, as have many other unions, accounting in total for 195 votes at today's conference.
Yesterday, the Association of Secondary School Teachers in Ireland said there had been an 82 per cent vote to reject the agreement.
Only 15 per cent of its members entitled to take part in the ballot actually voted on the agreement, which the union claims failed to address key issues such as the under-funding of second-level education, overcrowding in classrooms, under-resourcing of science education and a lack of emphasis on special education needs. The Teachers' Union of Ireland has also rejected the agreement in a members' ballot.
Today's conference will be formally opened by the president of Ictu, Peter McLoone, followed by a speech by David Begg, Ictu's general secretary.
Under the Ictu constitution, delegate places are allocated to the conference according to a union's number of members.
However, the system is weighted so as to enable smaller unions to send more delegates per 1,000 members than the largest unions. Mandate, which represents 25,000 workers in the retail and bar trades, is one of the largest unions opposed to the agreement. It has said that the pay increases promised in the agreement will be negated by increases in inflation.
Last weekend, the Irish Nurses' Organisation decided not to attend today's conference following its members' decision not to indicate their position on Towards 2016 until they received a decision from a recent Labour Court hearing on a pay claim.
The national partnership agreement centres on a 10 per cent pay increase in four phases over 27 months. It also contains an additional half per cent increase for those earning €10.25 per hour or less, and new legislation to prevent employers from making people redundant in order to replace them with cheaper labour. In addition, a Green Paper is to be published within 12 months and an office of director for employment rights compliance is to be established which will be staffed by 90 labour inspectors.
New penalties are also to be implemented of up to €250,000 and/or a prison term for breaches of employment law.
