The bigger public sector unions such as Siptu and Impact are confident they will get the controversial public service pay agreement over the line despite vocal opposition to the deal last week from the two teacher unions, the ASTI and the TUI.

While no formal decision has been made yet, it is understood that once all the unions have completed their ballots on the deal, the powerful public services committee of ICTU will meet to make an overall decision which, critically, will be based on the relative strength of each union.

Siptu and Impact, both of which have said the deal is the best that can be secured in current circumstances, represent almost half of the 250,000 public servants and, accordingly, half the votes at ICTU.

Jack O'Connor of Siptu said last week that the deal represented the most that can be achieved in such unique times as the country faces bankruptcy. Tom Geraghty, head of the Public Service Executive Union (PSEU), said rejecting the deal would leave public servants vulnerable to further pay cuts.

Those votes alone would be almost enough to get the deal through, assuming that Siptu and Impact vote in favour. But they will be joined by the PSEU, which has 10,000 members, and the primary teachers union the INTO, which has 20,000 members. This virtually guarantees acceptance.

All unions must abide by an ICTU decision even if they voted against it. The alternative is to quit ICTU which would be seen as a drastic move.

Even traditionally militant unions such as the Civil Public & Services Union, which has been at the heart of the dispute in the passport office in the past week, and the nurses union the INMO, have stopped short of openly criticising the deal, preferring instead to allow their members to decide in a ballot.