Mr Watt was asked about the €292,000 salary at a meeting of the Public Accounts Committee (PAC).
However, he said he was not answering the question, saying it was not the matter he was before TDs to discuss and citing rules that limit what committee members can ask.
The PAC and the Committee on Finance previously examined the issue of senior executives’ pay in the public service.
This was prompted by questions over the processes involved in Mr Watt’s appointment to the job on an interim basis last January pending an open competition for the permanent role.
A report, published last month, found that the interim appointment and salary increase were arranged in an “ad hoc fashion following discussions among a small number of senior officials and members of the Government”.
The report added: “The committee is of the firm view that operating in this manner has damaged public trust and eroded confidence in the system of public administration.”
Mr Watt, a former secretary general of the Department of Public Expenditure and Reform, was successful in the competition for the permanent role at the Department of Health and was appointed in April.
Mr Watt said at the time he would waive what amounted to an €81,000 salary increase over his previous pay “until the economy begins to recover and unemployment falls”.
At the PAC, Sinn Féin TD Matt Carthy asked him if he is continuing to waive the salary increase and whether or not he believes the overall €292,000 salary is “appropriate and warranted”.
Mr Watt said he was asked to go to the PAC to talk about the Department of Health’s 2020 accounts, a value for money review relating to nursing homes and the National Children’s Hospital project.
Committee chairman Brian Stanley said, “If you’re happy enough to answer the question from the deputy I’d ask you to”, but added: “You don’t have to answer it either.”
Mr Watt replied: “So you’re allowing the question to stand chair, is that what you’re saying? So I can answer the question or not. I wasn’t brought here to talk about these matters.”
He added: “Your standing orders I think are very clear about this matter now, about what I’m asked and what I’m not allowed to be asked. So I’m not answering the question.”
Mr Stanley said: “That’s okay.” Mr Watt said: “I’ve commented on this before and I have no further comment to make on it.”
Mr Stanley said he was free to answer the question if he wished but “I can’t compel you to answer the question because it wasn’t on the invitation. That’s exactly the point I was making.”
Another Sinn Féin TD Imelda Munster later said in her contribution it was “a bit of a touchy subject there Mr Watt, in relation to your salary”.
She began asking the Comptroller and Auditor General (C&AG) Seamus McCarthy a question but Mr Watt interjected saying: “I’m here to answer questions Deputy in terms of my duties . . . with all due respect.”
Ms Munster asked the C&AG if it would be in order to discuss the salary for the secretary general role in 2020.
Mr McCarthy said: “I don’t think it’s for me, Deputy, to say what is appropriate for questioning at the PAC.”
Mr Stanley said: “We’ve dealt with that issue of the income.” Ms Munster said: “Okay, we could maybe discuss it as part of the 2021 accounts in a few weeks perhaps.”