The NHS will "fail" if it continues to deliver the same services, but for less money, according to the director of the Welsh NHS Confederation.
The finance committee were taking evidence on the Welsh Government draft budget 2012-2013, on 20 October 2011.
According to Helen Birtwhistle the health service is facing increasing pressures to maintain the same level of services on a tight budget.
Ms Birtwhistle said: "I have thought long and hard, I have to make people realise the seriousness of the situation.
She stressed: "The NHS cannot provide good services in Wales on a reduced budget."
The director warned that "tough choices" would have to be made and that "change is inevitable", but insisted engaging the public of these changes were a priority.
However, Chair Jocelyn Davies accused the NHS confederation of "giving entirely the wrong impression" over the previous years that "no material changes" would be made to future public services, despite tighter budgets.
The current director denied any knowledge of these comments made during previous assembly committees.
Helen Birtwhistle also signalled that changes would be made to local services such as district general hospitals.
She said: "Hospitals are not the be all and end all.
"We have to help the public recognise and give them the confidence that the NHS can do things in a different way."
The committee also listened to evidence from Local Government and Communities Minister Carl Sargeant who denied that the Welsh Local Government Association had rejected plans for collaboration between local authorities in Wales.
In September 2011, the Welsh Government revealed a blueprint for radical reform of local government.
It wants six new regional groups to run services such as education and social care, rather than the 22 local authorities.
Carl Sargeant expressed his confidence that local authorities would be able to provide improved local services across Wales in a more cost effective way.
The minister rejected claims from the Liberal Democrat AM Peter Black that the Welsh Local Government Association (WLGA) were unhappy with the future collaboration of local authorities.
Mr Sargeant insisted that there was "clear support" from the leader of the WLGA, who said he was in favour of regionalisation.
The minister said: "I genuinely believe that the 22 local authorities across Wales can work together, but they must do it in a cost effective way."
He added: "There are examples of good practice of this throughout Wales as joint services are currently being operated well between local authorities."
Read this in Welsh.