A record number of 17,885 people were in emergency accommodation last month, according to the Department of Housing.
The number of adults in emergency accommodation now stands at 12,055, with 5,830 children in emergency accommodation.
This compares to 17,527 people in July, an increase of 358 people.
In July, there were 5,659 children availing of emergency accommodation, which represents an increase of 171 children.
David Carroll, Chief Executive of Depaul, said that now is the time for bold action as homeless numbers rise once again.
"There is a tangible frustration among those working on the frontline at what is starting to feel like an acceptance and business as usual attitude by those with the responsibility and power to bring about change.
"We cannot sleepwalk into accepting these or any homelessness figures as our new normal.
"We believe to truly end homelessness, we must combine increased housing supply with the mental health, addiction and community supports people need to build stable lives and become part of thriving communities."
Simon Communities of Ireland called on Government to make homeless prevention a priority in Budget 2027.
"Budget 2027 is an opportunity for Government to demonstrate that preventing homelessness is a national priority," Ber Grogan, Executive Director of the Simon Communities of Ireland said.
"We need investment in the services and supports that can intervene early, before even more people are forced to experience the trauma of homelessness," he added.
Focus Ireland CEO Pat Dennigan echoed those calls, saying in the upcoming Budget, the Government must continue to accelerate housing delivery while also strengthening homelessness prevention measures.
"These figures are not just statistics, these figures represent 17,885 human beings who are currently experiencing homelessness, including families with children living in emergency accommodation.
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"While significant efforts are being made across the sector, it is clear more action is needed if we are to reduce the number of people entering homelessness and increase the number leaving it.
"Keeping people in their homes wherever possible remains one of the most effective ways of tackling homelessness and this requires increasing the HAP support payment," he said.
Sinn Féin TD Eoin Ó Broin also called for an increase in the Budget for homeless prevention.
"We need change and we need it now," he said.
He said the numbers are "going in the wrong direction", adding this crisis will worsen unless the Government takes action.
SocDems TD Rory Hearne says figures 'unacceptable'
Social Democrats TD Rory Hearne called the figures a "record high" and "unacceptable".
Minister for Housing James Browne said he does not want these homelessness figures to be "normalised".
"One person having to access homeless supports and services is one too many.
"Let me be clear that I do not find it acceptable and I don't want these figures to be normalised by the system, the state or by society."
He said he is "being relentless in doing what I can do to accelerate the available supply of public housing and more supply of all types so that people can exit homelessness into secure tenancies, as well as prevent people ever ending up in that situation".
"As Minister for Housing, I am treating this with urgency and I want people out of homelessness services as rapidly as possible, particularly children," he added.
Labour TD Conor Sheehan criticised "repeated failures from Fianna Fáil from Fine Gael".
Speaking outside Leinster House, he accused Minister Browne of "bluff and blunder" over the number of homeless people in this country.
"There is no urgency" from the Government to tackle homelessness, he added.
