A member of the Sláintecare Implementation Advisory Council has called for a meeting with Minister for Health Stephen Donnelly at the earliest opportunity in the wake of the resignations of two senior members of the group.
Speaking on RTÉ's Six One News, Dr Eddie Molloy said it will be difficult to replace the pair unless the Minister knows what happened.
It comes after 11 members of the council expressed "shock, regret and concern" at the resignations of two senior members of the health reform programme.
The council members said they were seeking answers from the Minister for Health and his department regarding the events that led up to the resignations.
"In light of these developments, as members of SIAC, we urge the Government to ensure the Sláintecare programme of reforms is implemented in word, deed and spirit," the members said.
Laura Magahy and Professor Tom Keane both stood down on Wednesday.
Prof Keane said he had "come to conclude that the requirements for implementing this unprecedented programme for change are seriously lacking".
The council members also expressed their "sincere thanks to Laura Magahy and Prof Keane for their leadership, professionalism and tireless work on Sláintecare".
Four current serving members of the council did not sign up to the statement.
Earlier, Dr Molloy said the departure of Prof Keane and Ms Magahy is a "very big setback".
"They had the support of a very diverse 20-member commission", he said. "They were moving along, they were driving a lot of innovation. People of their stature... to stand down, it's just very serious."
Speaking on RTÉ's News at One, he said: "I think it is a very big crunch point" ... "but I don't know what particular encounters that Tom and Laura had that led them to walk away."
Dr Molloy said it is "very likely" that the number who would have supported the statement would be "far more than 11" because the statement had been assembled in the last 12 hours.
He said even his own name was not on it when it was initially published.
"There's overwhelming support within the commission for this", he said.
Dr Molloy said that for over a year, the unanimous view of the members of the commission was that the regional structures should be moved forward.
He said members of the commission had Prof Keane and Ms Magahy write formally to the minister "pleading with him" to move this along.
"But he contested the advice of the commission", Dr Molloy said. He said the minister had expressed reservations that this structural change not take place during the pandemic. However, he added that those urging it included senior clinicians who had spent long hours at the coalface of Covid-19.
He said there is "new money coming as we speak" to support Sláintecare, adding that new money should never be put into "dysfunctional structures" because it should be used to incentivise changes.
Dr Molloy said that maintaining the central monolithic structure is a major inhibitor to fulfilling the promise of Sláintecare. He said that whenever there is decentralisation or devolution from a large monolithic, centrally controlled institution, the result should be a very lean centre and this has implications for a lot of people at the apex of the system.
Earlier, Taoiseach Micheál Martin said he would like to meet both to get a sense of their concerns and gain perspective.
At the Fianna Fáil think-in today, Minister for Health Stephen Donnelly said he is very sorry to see Ms Magahy and Prof Keane go and said both have done a fantastic job.
The minister said the mission to achieve universal health care must continue.
He added the waiting lists are "top priority".
Separately, an unpublished progress report for Sláintecare for the first six months of this year has highlighted that is has not yet been possible to agree a multi-annual plan to cut waiting lists.
The 21-page report, seen by RTÉ News, identified waiting lists as one of three areas where there are significant challenges to progress.
Progress on setting up Regional Health Authorities is also highlighted as being delayed and rolling out eHealth and Information Communications Technology in the HSE has been significantly affected by the cyber attack.
These three areas are highlighted in red as facing significant challenge.
The report says a significant challenge is progress on establishing Regional Health Authorities, so that a business case can be sent to Government for approval.
It says that revisions are continuing in light of feedback from Department of Health stakeholders and engagement with the HSE, clinicians, and patient representatives has been delayed due to competing cyber attack and pandemic priorities.
The progress report also highlights some plans facing "minor challenges". Of the 929 extra acute hospital beds to be put in place, 834 have been opened.
Of the 43 extra ICU beds due to be operational, 40 are in place.
The report says there have been some minor challenges in rolling out increased home supports and devising a plan for the three new elective hospitals in Dublin, Cork and Galway.
Overall, the review says that of 112 'deliverables', 84 are on track, 25 face minor challenges and three face significant challenges.