NI's deputy first minister has said the health minister is acting too slowly in key areas such as testing and providing protective equipment to health staff battling coronavirus.
Sinn Féin's Michelle O'Neill accused the UUP's Robin Swann of "slavishly following the Boris Johnson model".
But First Minister Arlene Foster said she had confidence in Mr Swann and that it was "not a time for party politics".
Mrs Foster denied co-operation within the executive had collapsed.
#Coronavirus : Deputy First Minister @moneillsf tells @MarkCarruthers7 she thinks the NI @healthdpt & Minister @RobinSwannMoH have been too slow to act.— bbctheview (@bbctheview) April 2, 2020
You can see the full interview on @BBCTheView at 10.50pm - followed by analysis from @mlchealth & @markdevenport pic.twitter.com/8VUOfNy5ZH
A total of 48 people with Covid-19 have died in Northern Ireland.
Some 7,500 tests have confirmed 904 cases across NI, with 130 new cases confirmed on Thursday - a 17% day-on-day rise - prompting calls for testing to be ramped up.
In the UK, 3,605 people (out of 38,168 who tested positive) have died - with 684 more fatalities reported on Friday - while there have been 98 fatalities and 3,849 confirmed cases in the Republic of Ireland.
There are now more than one million confirmed cases of the coronavirus worldwide, with estimates suggesting more than 50,000 people have died.
'Slavishly following' Johnson
While Ms O'Neill said she was committed to working with Mr Swann, she said the rate of daily testing in Northern Ireland - some 500 people out of a targeted 1,100 - was well below the required rate.
"Slavishly following the [UK Prime Minister] Boris Johnson model, which has been too slow to act, means we are not as prepared as we could be," Mrs O'Neill told BBC NI's The View.
"I have made these arguments privately and I feel it's my moral duty, given the severity of the situation we are dealing with, that I have to say those things when I think they are not right.
Ms O'Neill said her stance was not about party politics, but saving lives, and insisted the executive was "working together" to address the issues.
"This is about what is the best advice - the World Health Organisation has very clearly said: 'Test, test test.'
Mrs Foster said the fact the deputy first minister had made the comments publicly was "a matter for her".
"I have to support all of my ministers, because that is what we have to deal with at a very difficult time for us all," the first minister told the Good Morning Ulster radio programme.
"We have to collectively work together to make sure I put our best foot forward."
UUP leader Steve Aiken said Mrs O'Neill was trying to exploit the crisis for political gain, adding that her comments were "regrettable but not unexpected".
"It is regrettable but not unexpected that the deputy first minister and Sinn Féin continue to seek to gain political advantage rather than joining together with the rest of the executive's political parties to do what is best for us all," he said.
Power-sharing at Stormont was restored in January, after a deal reached by the biggest unionist party, the DUP, and biggest nationalist party Sinn Féin, to end three years without a devolved government.
In another development, the diagnostics company Randox says its Covid-19 tasting kits are now "directly available" in Northern Ireland.
The Stormont health committee was told on Thursday the company was part of a UK-wide agreement which would see its product being sent to a central pool in England to be redistributed from there.
In a statement on Friday, Randox said after getting approval for its kits, the company made the case to the relevant statutory agencies that tests should be made available locally.
The BBC understands the Randox tests will be used beginning this weekend to test healthcare workers at the NI site at the SSE arena. It's part of the UK-wide initiative.
Over the years, the clarion call in NI has been for politics to be taken out of health.
But if the parties failed to do that in the past, how can anyone expect them to take the politics out of a pandemic?
Michelle O'Neill's latest comments will not do anything to bolster the idea that the executive she co-leads is working to the concept of collective responsibility.
Sinn Féin argues that if it tried to solve its differences with other parties behind the scenes - rather than airing legitimate problems with strategy in public - it would get slated.
However, critics have accused the deputy first minister of looking more like an opposition leader and playing politics, than the joint head of an administration speaking out on principle.
First Minister Arlene Foster sounded a calm note in her interview this morning, but at what point do the differences in approach become too much to bear?
For weeks now, all has not been smooth within the executive and it doesn't seem there's a chance of putting this back in a box.
More kit required
Ms O'Neill also said more must be done to provide personal protection equipment (PPE) to front-line healthcare workers.
On Thursday, Royal College of Nursing Director Pat Cullen said nurses were concerned at the lack of equipment and the transfer of testing kits from Northern Ireland to Great Britain.
Mr Swann had insisted both testing and PPE were key priorities for his department, but added there was no "quick fix".
"The situation with PPE supply has been made more challenging by the fact that supply routes from China, a leading global provider, were closed until recently," said Mr Swann on Thursday.
NI health officials have said they expect to hit the peak number of cases between 6 and 20 April, with an anticipated 3,000 deaths in a 20-week "first wave" of the coronavirus pandemic.
Expert modelling suggests 180 patients will need ventilation; Northern Ireland currently has 165 ventilators, more have been ordered and 650 units capable of providing respiratory support are also being procured.
Expert modelling also indicated there could be second wave later in 2020 in the absence of a vaccine or sufficient population immunity.
In other developments:
- 17,000 jobs are to be furloughed in NI under the government's coronavirus job retention scheme
- 220 schools say they are prepared to open at Easter for the children of key workers and vulnerable children
- Key services are struggling with reduced staffing numbers - 10% in Belfast's health trust, nearly a quarter of prison workers and a third of community pharmacy staff - due to workers self-isolating
- Questions are being asked about Health Secretary Matt Hancock's pledge that 100,000 tests will be carried out every day by the end of April
- Belfast City Hospital is being transformed into NI's first Nightingale hospital, with a 230-bed unit for critically ill patients
- Testing centres are being prepared at Belfast's SSE arena in Belfast and MOT test centres
- A "clap for carers" brought people to their front doors across NI and the UK on Thursday night to show appreciation for health staff