The Tánaiste believes his own chief of staff in a dispute with the Department of Health's top civil servant on the botched Dr Tony Holohan secondment.
Micheál Martin has sided with his most senior adviser, Deirdre Gillane, who rejected an account provided by Department of Health secretary general Robert Watt to an independent investigation into Dr Holohan's abandoned Trinity College role.
In April 2022, Dr Holohan said he had decided not to proceed with his secondment as Professor of Public Health Leadership and Strategy at Trinity College. The secondment had been dogged by controversy over the salary arrangements and had been paused by Mr Martin the week previously.
Mr Watt, who was highly involved in arranging the secondment, claimed Ms Gillane had been informed of the details of the appointment.
However, the then chief of staff in the Department of An Taoiseach, said Mr Watt's claims that she had been fully informed were "wholly without foundation" describing his remarks as "inaccurate and unwarranted".
When asked whether he believed Mr Watt or Ms Gillane, the Tánaiste said: "In respect of the chief of staff in my office, Deirdre Gillane, obviously I think her presentation cannot be questioned, of course I believe what she said."
He added that Maura Quinn's report into how the appointment and the funding allocation was made is "very clear".
"The conclusions that arise out of it are very clear," Mr Martin said.
Health Minister Stephen Donnelly has also been called on to respond to the conflicting remarks of senior officials contained in the independent report.
Mr Donnelly is expected to be grilled on Dr Holohan's abandoned appointment when he appears before the Health Committee on Wednesday.
The independent report found that Dr Holohan should not have been personally involved in the negotiations with Trinity College and concluded that a €2m annual funding for the role by-passed all of the accepted research protocols.