The retiring members of the Sláintecare Implementation Advisory Council have written to the Taoiseach today.
They warn that the unexpected resignations of key people has caused concern that there are "fundamental obstacles" within the political and administrative systems, to successfully implement the reform plan.
The four-page letter, written by Liam Doran on behalf of the remaining members of the group, says that while there has been steady progress, difficult issues remain.
The group says that before they depart, they are available to meet with the Taoiseach and the other government leaders, should they wish, and remain available to assist in every way possible.
The letter says that the SIAC do not as yet understand the full reasons for the sudden departure of Professor Tom Keane and Laura Magahy.
It adds that plans to regionalise the health system into six areas is a critical enabler for Sláintecare but that in an acute pandemic, it is reasonable to defer it for administrative and other reasons.
Mr Doran said the view of the SIAC is that this reform should not be delayed any longer, given the State's successful vaccination campaign.
The letter says that when the Sláintecare Report was being written in 2017, there were almost 600,000 people on waiting lists.
Today, despite much investment and effort it says, the number exceeds 900,000.
SIAC also points to the importance of moving private medicine out of public hospitals and developing equitable access to GP care, without personal cost, or at low cost.
"Sláintecare is not a person, organisation or personal fiefdom. It is a policy, process and promised transaction between the State and its people. In fact, it is owned by the people and is for the people," the letter states.
The retiring members of the SIAC say they are now handing over this responsibility to a new oversight group, with a different governance structure, at a difficult time, following a period of unexpected upheaval at the heart of the Sláintecare team.