The Ulster Unionist Party will vote against Stormont’s budget which is being debated at the assembly.
The party’s Health Minster Robin Swann opposed the budget when it was agreed by other executive ministers in April.
During the debate on Tuesday, he said the budget would cause “serious and potentially irreparable damage” to health services.
Mr Swann, who is stepping down as health minister to stand in the UK general election, said the budget did not prioritise the “health of our people”.
The Ulster Unionist Party (UUP) wanted the assembly debate to be postponed until after a budget re-allocation exercise which is due to happen next month.
When the finance minister, Sinn Féin’s Caoimhe Archibald, announced the budget in April she allocated about £15bn for day-to-day spending and £2bn for infrastructure and investment.
Speaking during Tuesday’s debate, she said it was “always going to be an incredibly challenging budget” for the executive.
“For every pound we had to allocate for day-to-day spending for public services, we had three times as many demands,” Ms Archibald added.
The Sinn Féin minister criticised the “austerity agenda” of the Conservative government, but said recent negotiations with the UK Treasury meant concerns on future funding levels for Northern Ireland could be “tempered”.
Also during the debate, the SDLP’s Matthew O’Toole said the budget was “not a plan” for the future.
The leader of the opposition added “there was no reason why this budget statement couldn’t have been a more strategic, forward-looking set of priorities for how the executive was going to go about making decisions”.
According to BBC News NI’s business and economics editor John Campbell, there is “not much love” for this budget.
Even the finance minister acknowledged it will undoubtedly mean difficult decisions for all Stormont departments, he continued.
Those difficulties will be eased slightly in the next couple of weeks when the minister is able to allocate about £200m of new or unspent funds.
How much money do the departments get?
The Department of Health got the largest share of day-to-day funding (£7.8bn).
The next-largest allocations went to the Department of Education (£2.9bn) and the Department of Justice (£1.3bn).
The health budget was up by 6.3% compared to the opening position last year but was down by 2.3% when compared to what was actually spent by the end of last year.
Mr Swann said Northern Ireland’s devolved institutions must “make the very best use of the resources that we do have and protect the most vulnerable”.
“That is why I and so many patients and health service workers took reassurance from the public statements, both before and after the restoration of the executive, that the health of our people was going to be prioritised,” he said.
“I believe this budget does not achieve that.”
Mr Swann said that in voting against the budget, he acknowledged he would not be complying with the ministerial code.
“I don’t do that easily, but I have a greater responsibility to defend and protect vital services,” he said.
Is there any extra money?
When the budget was announced, Deputy First Minister Emma Little-Pengelly, of the Democratic Unionist Party (DUP), said she understood Mr Swann’s concerns, but there were other important priorities which required funding such as special educational needs.
There will be an additional £200m for the finance minister to distribute in a re-allocation exercise known as the June monitoring round.
That includes some money carried over from last year, additional money from Westminster and the start of a new ‘top-up’ procedure for Stormont’s budget which was agreed with the UK government.
The UUP leader Doug Beattie had wanted the budget debate to be postponed until after the monitoring round.
He said it had “the potential to ease some of the pressures we have highlighted in the existing health allocation”, adding that it “makes no sense for the Executive and Assembly to pass a budget that is almost certain to change within weeks”.