The UK variant of Covid-19 cannot be behaving differently in Northern Ireland from the Republic, Stormont's deputy First Minister said.
The highly-infectious mutation first discovered in southern England is becoming the dominant one in the Republic and helped produce an enormous post-Christmas spike in infection, medics believe.
Taoiseach Micheál Martin has said Northern Ireland is not testing enough for it.
Michelle O'Neill said she wanted to see greater cooperation across these islands.
She added there was no intention to "take a swipe" at anyone but recognised an anomaly since the variant had been identified as spreading rapidly in the Republic.
She said: "That needs to be resolved.
"I cannot see how the new variant is behaving any differently.
"We need proper identification of the variant."
She said health minister Robin Swann would bring Stormont's Executive up to date on the matter during its meeting this week.
She added better cooperation during the pandemic between the two islands would produce a far better situation and called for a meeting of the British/Irish Council.
"I would much prefer we did it across the two islands."
First Minister Arlene Foster said she also spoke with the Taoiseach and he accepted that Northern Ireland was testing for Covid-19.
She added: "The variant testing here is massively more advanced than Republic of Ireland."
She said she pressed Mr Martin on sharing travel locator forms.
"He committed to movement soon on that issue."
Thomas Buchanan of the DUP told the Assembly the Taoiseach made "disgraceful" comments.
Ms O'Neill called for a "two-island approach to travel".
"I am hopeful that there will be resolution to that mandatory quarantine in terms of people travelling in."
The Department of Health has said there is "complex and specialised" work going on in Northern Ireland on whole genome sequencing (WGS) which allows scientists to examine the DNA of viruses.
It said: "To suggest that Northern Ireland is inactive in this field would be wholly incorrect - and is unfair to the dedicated, expert local staff working intensively in this area.
"Work is ongoing in relation to increasing the level of publicly available data on the 'B.1.1.7 variant' in Northern Ireland.
"In addition to whole genome sequencing, the prevalence of the 'B.1.1.7 variant' in the UK regions, including Northern Ireland, is being monitored via PCR testing data - and reported on publicly by the Office for National Statistics."
The sharing of travel locator forms for people arriving into the Republic then travelling north has been a long-running problem.
Ms O'Neill said she was hopeful of a resolution with the Republic's government over the data sharing issue.
She also said student nurses have been on the frontline throughout this pandemic and Sinn Féin was proposing the health minister increased student nurse bursaries and that final year students were offered the opportunity to complete clinical placements as paid staff.
It is understood the Stormont leaders and the Taoiseach spoke about their approaches in tackling Covid-19.
A number of issues were raised, including the sharing of passenger data.
Mrs Foster and Ms O'Neill have previously criticised the Irish Government for failing to share information on travellers arriving on the island during the pandemic.
It is understood they had a discussion around the issue and are confident it will be resolved shortly.