The Irish Medical Organisation has passed an emergency motion at its annual conference in Killarney urging all members to vote No in its ballot on the Croke Park II proposals.
The motion said that should the Public Service Committee of ICTU accept the proposals on 17 April, the IMO would not be bound by the decision.
Meanwhile, the IMO has said it would have gone into liquidation if it had been forced to payout the €25m its former chief executive was entitled to.
Its outgoing president, Dr Paul McKeown, said that the payout "would have been fatal".
Delegates at the IMO annual conference are debating a series of motions in the aftermath of the controversial €9.7m retirement package for former CEO George McNeice.
Claims that the pay arrangements were widely known have been rejected at the conference.
A spokesperson for Mr McNeice has said that the details of his remuneration were clearly known within the IMO.
He also reportedly wrote to the organisation in 2008 asking to forgo further special bonus increases in light of the economic situation in the country.
The spokesperson said the former ceo did not wish to make any further comment at this stage.
Dr McKeown told delegates in Killarney that he hoped Mr McNeice would co-operate with an independent review that was being set up.
He said he was "disgusted" at the attempts to justify what he termed "excessive pay arrangements".
He also questioned the timing of comments attributed to a spokesman for Mr McNeice, coming at the start of the conference.
Earlier, Dr McKeown said former president Professor Joe Barry signed the contract for Mr McNeice in 2007.
Prof Barry has told RTÉ News that he looks forward to the external review.
He said the retrospective review had been organised and was happening fairly soon.
Dr McKeown said that Prof Barry was chairman of the IMO's remuneration committee, but did not appreciate the ramifications of the contract.
He described the signing as a "procedural matter" after Dr Cormac Macnamara had negotiated it, but died some time after.
Speaking on RTÉ’s News at One, Dr McKeown described the contract as a major mistake and a lack of oversight.
A spokesperson for Mr McNeice has said that details of his remuneration package were not a secret and that people within the union should have known.
Dr McKeown said when he was on the IMO management committee he was not aware of the contract details.
He said there was no sense of catastrophe in the union.
Dr McKeown said the results and recommendations from an external review should be known during the second half of the year.
Also at the conference, two AGM motions on abortion will call for support for regulation of abortion services where there is a real and substantive risk to the life of the mother.
Regulation will be discussed for abortion where a woman becomes pregnant due to a criminal act or where there is a non-viable foetal abnormality.
Non-consultant hospital doctors will highlight what they say are dangerously long working hours.
GPs will warn Minister for Health James Reilly against plans for further pay cuts to their fees for seeing medical card patients.