A total of 8,475 people were recorded as homeless in September, with children making up more than a quarter of those without a home in the State.
Department of Housing figures show there were 2,344 children living in emergency accommodation last month, with more than 1,800 in Dublin.
The number of homeless people in Ireland fell considerably during the early part of the Covid-19 pandemic, down from a peak of more than 10,500 in late 2019.
However, in recent months the numbers have started to rise again and an increase of 263 was recorded between August and September.
The department’s figures show 1,005 families were homeless in September, up from 953 the previous month. The majority of homeless families, 752, were in Dublin.
There were 6,131 homeless adults, two thirds of whom were men, with 2,113 women recorded as homeless.
The number of young homeless people has increased significantly in recent months, with 989 people aged 18-24 listed as homeless in the latest report. A total of 128 people aged 65 or older were recorded as being homeless last month.
Responding to the figures, Focus Ireland chief executive Pat Dennigan said said the charity for homeless people was "deeply concerned" to see the numbers "heading in the wrong direction".
“The progress that was made during the last two years is now being lost because we have stopped doing the things that worked – protecting renters and freezing rents,” he said.
Mr Dennigan said the country was facing “another winter in which many children will be spending Christmas in emergency accommodation”.
Wayne Stanley, head of policy at the Simon Communities, said the growing scale of the homelessness crisis was "shocking but not surprising".
One point of particular concern, he said, was a 10 per cent increase in family homelessness outside of Dublin, which pointed to the “deepening housing affordability crisis across Ireland”.
Pat Doyle, chief executive of the Peter McVerry Trust, said Covid-19 had "slowed down" a number of social housing developments, with some projects delayed by up to six months.
“This has a direct impact on homelessness as the number of housing pathways for people are reduced, leading to a rise in the overall homeless figures.”
Minister for Housing Darragh O'Brien said the further increase in homelessness figures was a "serious concern". He said he met local authority officials earlier this month, on foot of the growing numbers presenting as homeless.
The Minister said he intended to set up a national homeless action committee, which would bring together Government departments and other key bodies.
“While we have made significant improvements on the situation we were facing two years ago when homelessness was at its highest, there is still a huge amount of work to be done,” he said.