A total of 134 families became homeless in Dublin in January, according to Focus Ireland.
The figure of 134 homeless families - which includes 269 children - is an increase of 148% on the figure of 12 months previously and is the highest ever monthly increase in family homelessness.
The previous highest monthly was 84 families in August 2015.
Of the 134 families, 125 (with 253 children) were categorised as "newly" homeless by the Dublin Region Homeless Executive, meaning they had not been homeless during the previous two years.
The other nine families had been homeless at some point in the last two years, and returned to emergency accommodation in January after their new accommodation proved unsustainable.
The organisation has said that ending the homeless crisis must be a top priority for the next government.
Focus Ireland has called on the next Government to set a firm target date for ending family homelessness and to commit to building 40,000 social homes over the next five years.
The body's director of advocacy Mike Allen said: "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. The repossession of buy-to-let landlords, often by banks owned by the Irish people, is a growing phenomenon and may account for up to half the recent cases of family homelessness.
"There are over 35,000 buy-to-let landlords who are more than a year in arrears on their mortgages and we have been warning Government about this impending problem for over three years."
He added: "Focus Ireland welcomed the fact that Minister (for the Environment Alan) Kelly included this issue in his ‘20 point plan’ on homelessness in December 2014.
"However, no response whatsoever has been put in place to deal with the issue. The consequences of this inaction are now being felt by these families.
"Meanwhile, a second element is the crisis is rapidly increasing rent levels and the point blank refusal by the Government over recent years to increase the level of Rent supplement to match market levels. Rents have shot up by 30 or 40% and even more in recent years and last month a report found that 95% of all properties for rent were too expensive for rent supplement limits."
Pat Doyle CEO of Peter McVerry Trust said: "We really hope that this figure is a post Christmas spike and will not be a trend repeated for the rest of the year.
"However, looking back at last year, 47 families presented as homeless in January 2015 and that turned out to be second lowest figure recorded all year. If this figure of 125 new cases is repeated or even exceeded on a monthly basis throughout the year, the consequences would be enormous."