Almost a quarter of people in direct provision centres are still sharing a bedroom with non-family members.
That amounts to at least 1,700 asylum-seekers in facilities across the country.
The Irish Refugee Council says it is highly inappropriate during the coronavirus crisis.
The Council's chief executive Nick Henderson says it goes against health advice.
"It's deeply concerning," he said, "that sharing of intimate space like this should not be occurring.
"It is also, we believe, contrary to the legal advice that we have received at the Irish Refugee Council that states that the government should be taking steps to ensure that people have accommodation where they can socially distance," he added.
The legal opinion was drafted by prominent human rights lawyer and senior counsel Michael Lynn and barrister Cillian Bracken for the Irish Refugee Council.
The opinion was distributed widely by the Public Interest Law Alliance to NGOs earlier this month.