Some 134 families, including 269 children, presented to homelessness services in January.
Of these, 125 families, including 253 children, had never been homeless before.
The number of homeless children in Dublin now stands at 1,570, across 769 families.
This represents a 101 per cent increase in homeless children in the capital since January last year, when there were 780 children, across 493 families.
Mike Allen, director of advocacy with Focus, said the figures showed the “recovery” had not reached large swathes of the population.
“The continued massive rise in family homelessness is due to the prolonged crisis in the private rented sector.
“One key aspect of this crisis is lending agencies foreclosing on buy-to-let landlords and then evicting the tenants.”
Mr Allen said this was a crucial aspect of the crisis that had not been addressed in any way by the Government, despite measures taken in other areas.
He estimated up to half of newly homeless families were losing their rented home in the buy-to-let market.
Sam McGuinness, chief executive of Dublin Simon, said there was an “urgent need” to move away from emergency responses to the housing and homelessness crises.
“As rents remain unaffordable and the gap between rent supplement and market rents continues to widen, more and more children, families and individuals will be pushed into homelessness, especially at a time when the number of properties available to rent is at an all-time low.
“ Providing people with the support to stay in their homes, together with ensuring the provision of affordable housing, with support to move [people] out of homelessness, will be the only way we are going to solve this crisis long-term.”
Mr Allen said many families entering homelessness had been living with wider family immediately beforehand.
“For instance, many families who have lost their own home are often able to stay with their wider family for a period of time – especially at Christmas.
“Then when they have to leave the extended family’s home this can lead to the cause of their homelessness being wrongly interpreted as ‘family breakdown’.
“However, a deeper look at the stories of these families shows that they were only living with wider family because an earlier private rented sector tenancy had broken down for reasons such as they couldn’t afford to pay the rent or the banks had foreclosed on the landlord’s property.”
Of the 769 families in emergency accommodation in Dublin last month, 216 of them, with 429 children, were in supported homeless accommodation, while 553 families, including 1,141 children, were in hotels.
The previous highest number of newly homeless families was in August 2015, when 84 families presented to homelessness services.