Twoformer union figures due to be quizzed about a multimillion euro "slush fund" by the Dail's spending watchdog have claimed certain TDs are biased against them.
Ex-SIPTU official Matt Merrigan and a former member of the union's national executive, Jack Kelly, made the allegation in a letter to the Public Accounts Committee (PAC).
Writing on behalf of both men, Mr Merrigan claimed members of the committee had demonstrated they were "not free from subjective bias" and had already prejudged the matter.
The duo, who set up the training fund at the centre of the committee's investigation, have been seeking to have orders compelling them to give evidence on November 27 set aside. They risk being held in contempt of court if they refuse to appear.
Both men and former HSE employee Alan Smith face questions about how money from the State-funded account was used to pay for foreign trips for union members, civil servants, health officials and their spouses.
In the letter, Mr Merrigan said any questioning could prejudice a garda investigation into the administration of the fund. He also said the garda probe could be prejudiced if he is forced to hand over a report by Grant Thornton on the issue.
Mr Merrigan claimed the report, which he commissioned "for the advice of my legal advisors", was a privileged document that would not be admissible in any court.
He also claimed it was "not within the competence of the committee" under Dail standing orders to investigate the fund as it was not audited by the Comptroller and Auditor General.
Under the standing orders, the PAC is mandated to examine bodies which are audited by the C&AG. However, the committee has examined a number of bodies not audited by the C&AG.
Should the witnesses fail to appear, the PAC can ask a court to hold them in contempt.
The PAC took legal advice on the contents of Mr Merrigan's letter yesterday and is to respond to the points raised.
The fund, known as the health and local authority account, was set up in 1998 and received €4.4m from the Department of Health, the HSE, a health service partnership forum, and a local authority partnership body.
It was to to train lower-grade workers in health services. However, some of the funding was used to pay for trips to over 70 foreign destinations, including the US and Australia.