The Chief Medical Officer, Dr Tony Holohan, has said results of antigen tests carried out by the public cannot be relied upon.
He said the use of these tests by the general public is "strongly recommended against" by the National Public Health Emergency Team (NPHET).
He told a media briefing that antigen testing used in "controlled, appropriate circumstances" can have "an important role to play".
But, he added, results gained by carrying out such tests in general circumstances "cannot be relied upon". Earlier today, Tánaiste Leo Varadkar urged more employers to use antigen testing, but not as a substitute for other public health precautions.