The Fiscal Advisory Council has said the Government should stick to its previously published plan for a Budget-day package of €800m.
In its pre-Budget statement published today, the FAC said anything above this level should be paid for by tax rises or re-allocating existing expenditure.
The Summer Economic Statement said the Budget-day package - spending increases or tax cuts not previously announced - would be about €800m.
The FAC said the Government should stick to that plan, and not go beyond it. If it does want to spend more, then it should do so by raising revenues.
Echoing the Governor of the Central Bank, Philip Lane, it said stronger than expected growth and higher corporation tax receipts should be used to run a Budget surplus to prepare for the next downturn, which it describes as inevitable.
It said yet another overspend on the health budget would require additional funding this year, but said the money should come from savings in other departments, not extra spending, which is already running ahead of revenue growth.
It said staff recruitment costs have been blamed for the health overspend, but adds that those costs should have been planned for.
Chair of the Fiscal Advisory Council Seamus Coffey, speaking on RTÉ's Morning Ireland, said that economic recovery would not continue forever and we were in danger of "spending the money as quickly as it is coming in".
He said improvements on budgetary fronts have slowed since 2017.
Mr Coffey said the Government could continue to grow resources by increasing taxes in some areas and balancing the measures introduced in Budget 2019.
He said that in the medium and long-term Brexit and changes in international trade and tax rules could move against Ireland.
The economic recovery has moved faster than expected, he said, and more workers were needed, which links into the housing problems needed to attract workers.