The Irish Medical Organisation's 5,000 members have voted not to commission an independent review of the circumstances under which their former General Secretary George McNeice ended up with pension entitlements worth almost €25m.
Mr McNeice subsequently agreed to reduce his entitlement to €10m, when he retired in late 2012 at the age of 52.
In early 2013, members held an extraordinary general meeting and voted to carry out a retrospective review, but a year ago, the IMO's governing council decided to defer the planned review.
The council raised concerns about the potential cost and legal consequences of the review.
However, last April the IMO Annual Conference decided that the full 5,000-strong membership should be balloted on the matter.
Tonight's vote was close, with 52% opposing a review, and 48% in favour.
Sources said that a critical issue in the ballot was the potential cost of an independent review, which could have been between €200,000 and €1m.
They also noted that there was a likelihood of a legal challenge to any findings, which could prevent publication of the outcome.
IMO President Trevor Duffy said the closeness of the vote reflected the seriousness of the issue they were considering, but said the union's Council would respect the outcome of the vote.
He said they readily acknowledged the shortcomings and failings which had taken place in the organisation but said they had addressed them and undertaken very important reforms.
They included an extensive consultation with members, the adoption of a new set of rules, and the introduction of a new management and governance structure for the organisation which reflect the lessons learnt through this whole episode.
However, the ballot result means that the facts surrounding this controversial pension arrangement may never be revealed to the 5,000 union members.
