Focus Ireland says family homelessness outside Dublin is at 'unprecedented levels', having risen for the sixth year in a row.
It's launched its annual review - which says there are 9,968 people homeless across the country.
The charity worked with over 15,000 people during 2018.
"This year is seeing the largest ever increase in family homelessness", the report says.
"While a significant number of individuals and families have been supported to move on from homelessness, there have been a number of challenges that has seen homelessness increase again this year to new record highs".
These have included a reduction in allocations by some local authorities, and the housing crisis - which the charity says has led to increasing tightening of the private rental market.
Source: Focus Ireland
While the number of families entering homelessness increased.
The majority of those in emergency accommodation are in Dublin (67%) - but this has also increased outside the capital.
Focus Ireland says: "The reclassification of a significant percentage of families experiencing homelessness in 2018 has hidden the true scale of the increase in homelessness."
According to official figures, family homelessness has increased by 23% from the end of December 2017 to the end of November this year.
However when those families who've been 'reclassified' out of official numbers are included, family homelessness has risen by 53%.
Source: Focus Ireland
Spokesperson for Focus Ireland, Roughan MacNamara, is urging the Government to take more action.
"Once again homelessness has risen.
"Family homelessness has risen for the sixth year in a row, and we're seeing record numbers of nearly 10,000 people homeless - that's nearly 4,000 children.
"And Focus Ireland is really calling for significant Government action in the new year to tackle this ever-rising issue".
