The country's largest trade union is backing the Government's plan to cut the public service pay and pensions bill by one billion euro.
Siptu, which has 63,000 members in the sector, said the pay deal was the only way to stop vulnerable groups being isolated and attacked in the desperate quest for savings.
As its national executive met at Liberty Hall to consider accepting the Croke Park extension deal, the 24/7 Frontline Services Alliance met TDs and senators at the Dail.
The group, that represents nurses, gardai and firemen, claims a report shows frontline workers face cuts of up to 11.4% if the government proposal is accepted. A 24/7 spokesman said: "If anyone had any doubts about which way to vote then this report will make up their mind.
"The simple facts emerging from this study show the real cuts in pay and conditions. It is absolutely vital that Croke Park II is voted down."
However Siptu maintained the cuts were the best that could be obtained after unprecedentedly difficult negotiations.
"Voting no will not make the problem go away," said Siptu in a statement. "The Croke Park agreement will collapse and we will still be faced with the cuts agenda without the protections it provides. The country is subject to the Troika-imposed schedule for reducing the deficit, which is still the highest in the Eurozone.
"That entails cutting the gap between tax revenue and spending by a further 4bn euro to 5bn euro between now and 2015. Public Service pay and pensions account for 35% of all state spending."
The proposal, which includes pay cuts for staff on over 65,000 euro a year, increment freezes, longer working hours and reductions in overtime and premium rates, has been backed by Impact and the Public Service Executive Union. However several unions and organisations representing doctors, nurses, some teachers, higher civil servants and gardai are against the cuts.
Siptu plans to ballot members within weeks, including the 35,000 people in the health service, including porters and catering staff, as well as some staff in universities and local authorities.