There are no lateral flow tests available to order online as demand grows ahead of the Christmas holidays.
A shortage of the tests could spell disaster for people relying on them to access social venues or as reassurance to visit vulnerable loved ones over Christmas.
Officials have asked the public to take the rapid flow tests before going anywhere where there may be crowds of people as Omicron continues to take hold in Northern Ireland.
Proof of a negative lateral flow test is also required by anyone who is medically exempt from vaccination, or who has not been vaccinated, or who has recently recovered from a Covid-19 infection under the Covid certificate scheme.
Newly reported cases of the variant in Northern Ireland surged from 1,281 on Saturday to 2,349 on Sunday and it is expected to be the dominant strain here by the weekend.
Sinn Fein MLA Colm Gildernew, who is chair of the Stormont health committee, said: “I would urge the Department of Health to do everything they can so that people can get the tests they need to stay safe and access services.
“I welcome the fact that people are taking responsibility by taking the lateral flow tests, but when that’s the case, it is even more important that the Department of Health ensures they are freely available to those who want and need them.”
Lateral flow tests are available for free from high street pharmacies or by ordering them from the gov.uk website and are normally delivered within 24-hours.
However, from Monday night, the government website reported “there are no home delivery slots left for these tests right now”.
The tests were still unavailable to order on Tuesday morning.
It is unclear whether the issue is as a result of a lack of delivery capacity or a shortage of tests, however, some people have reported difficulties finding test kits in pharmacies.
A spokesperson for the Department of Health said: “There is a sufficient stock of lateral flow tests in Northern Ireland to supply local collection sites, including community pharmacies.
“Due to exceptional demand individual collection sites may at times run low on stock between deliveries. People are encouraged to try another site close to them. Additional deliveries of test kits continue to be made to Northern Ireland
“The quickest way to get free rapid lateral flow tests is from pharmacies and other local collection sites. To find a collection location close to you, go to the site finder online at https://maps.test-and-trace.nhs.uk/.
“There are more than 580 collection sites across Northern Ireland, including more than 500 community pharmacies. You can also order tests online at https://www.gov.uk/order-coronavirus-rapid-lateral-flow-tests.”
Meanwhile, the Executive is expected to receive a further briefing on Tuesday over the threat posed by Omicron.
Cases are continuing to rise, with the seven-day case rate in Northern Ireland spiking on Monday from 11,899 to 14,632.
The regular use of lateral flow tests has been recommended by health officials as part of a swathe of measures to try and slow the spread of Covid-19 in the run up to Christmas.
Lateral flow tests should only be used by people who are asymptomatic to indicate they do not have Covid-19 but should not be relied upon as a diagnostic tool.
Anyone with symptoms should book a PCR test and isolate until they receive a negative result.
Anyone with a positive lateral flow test is also asked to book a PCR test to confirm the infection.
It comes as efforts to vaccinate as many people as possible are ramped up with the opening of a new mass vaccination centre in Belfast on Tuesday.
The Titanic Exhibition Centre on Queen’s Road will offer booster, first and second doses of the Pfizer-BioNTech vaccine by appointment and on a walk-in basis from 8am to 8pm seven days a week.
The centre will close on Christmas Day and Boxing Day, with staff expected to administer up to 4,000 vaccines a day.
The centre is open to all age groups, with the 15-minute wait after vaccination paused for everyone except those aged 12 to 17.