The Health Service Executive says its overall deficit this year could hit €1.4 billion.
Its chief executive Bernard Gloster said it faces a cash deficit of just over €1.1bn for 2023.
He told the Oireachtas Committee on Health: "I would anticipate that the cash pressure for the HSE coming to the year end would be somewhere in the region of €1.1bn."
However, Mr Gloster said the overall deficit - involving income and expenditure - would increase it.
The committee also heard that to date, 622 consultants have signed up to the new public-only contracts, Department of Health Secretary General Robert Watt said.
He added that 160 of these were "new entrants".
Both men were answering questions from Sinn Féin's health spokesperson David Cullinane, who noted that the most recent projected overrun at the HSE for 2023 was €700m, a figure given at the end of July.
Mr Watt said that the cross-party support for the consultants contract "really did help" to deliver results.
"We're very happy it's going in the right direction," he said, adding that "we are seeing steady progress".
Mr Watt conceded the Government has "to do better when it comes to financial planning".
"This relationship between the budget and the [HSE] service plan needs to change, deputy, it's not fit for purpose," he told Mr Cullinane.
"This year has been exceptional and the level of demand way above what we thought" and "the inflationary environment" has also been a problem, he said.
Mr Cullinane quoted "minutes for the ministerial briefing for March 2023", which referenced the HSE National Service Plan that had been submitted to Minister for Health Stephen Donnelly in November 2022.
The HSE had estimated that the overrun would be "over a billion", while the department believed "that the real figure was somewhere between €400m and €500m," which the TD said "was grossly inaccurate".
Attempts to 'massage the figures' - Shortall
Social Democrats TD Róisín Shortall said that, earlier this year, the committee had witnessed "attempts to massage the figures" that were "outrageous" and an effort to "pretend that there wasn't a €2bn black hole within the [national] service plan (NSP)".
"We know the service plan was delayed, put back for three months or even more. As a result of this, we saw the back and forth between the secretary general and the then CEO of the HSE.
"So, you know, these are funny figures to a large extent. I would be surprised if the deficit at the end of the year is only €1.1bn," she said.
Mr Cullinane noted that, when it was delivered, "the revised NSP continues to highlight the material level of financial risk for 2023".
But he said the Department of Health was "directing to the minister that any reference to financial risk be removed from the National Service Plan".
This is "an unacceptable way to approach this," Mr Cullinane said.
Mr Watt replied: "Funding shortfall is different to financial risk."
"You're dancing on the head of a pin here," Mr Cullinane responded.
"There was a difference of opinion around financial risk," Mr Watt said.
Mr Gloster rejected claims that he was slow to contact private hospitals to secure extra capacity to deal with a "surge" in demand during the winter months.
"I don't accept the position that we're just too late in engaging with them," he told the committee.
"I don't simply accept that we turned up last week and picked up the phone and asked him for beds," he said, referring to the head of the Private Health Association (PHA).
Mr Gloster was responding to Fine Gael Deputy Colm Burke who said that "we've already heard from the private hospitals about engagement being too late".
"A number of my officials have met with them several times," the HSE chief replied, and pointed to a briefing given to the PHA last week.
"And I do want to be very careful, because we've just set the commencement of a particular process within the procurement framework to deal with that," Mr Gloster added.
"We're issuing a framework to the Private Health Association, which they had a pre-procurement briefing on last week," he said. "And that's for the additional surge capacity for the period November, December, January, February."
In March, the HSE was "using an average of 160 beats a day from the private hospital sector, since the end of - if you want to call it - the crisis or pressures of last February, and we agreed to continue that to next February," he said.
But Mr Gloster noted that "we have committed to - at the end of February next year - a review in the efficacy and the appropriateness of all of those beds, and what impact they're having on our system".
"We're spending serious, serious millions of money every quarter," he said, adding that he must "protect the public interest" in how the tax payers' money is spent.