Nationwide figures show there were 1,173 families and 2,426 children homeless in September
Focus Ireland says the number of homeless families in Dublin has surpassed 1,000 for the first time.
The charity's figures show that 65 families became newly homeless in the city in September.
It brings the total to 736 families - including 1,389 children - having become homeless in Dublin in the first nine months 2016.
Meanwhile, national figures released by the Government this evening show there are a total of 6,709 people homeless nationwide. That includes 1,173 families and 2,426 children in emergency or temporary accomodation.
Focus Ireland Director of Advocacy, Mike Allen, said: “We need to stop the constant flow of families and single people becoming homeless. Our frontline staff have seen first-hand that the two key reasons families are becoming homeless is one, landlords are selling up and getting out of the business, and two, rising rents.
"Both these issues are within the power of the Government to tackle and while they have taken some actions they have clearly not done enough, fast enough," he added.
Sinn Féin housing spokesperson Éoin Ó Broin, meanwhile, said the latest figures are "not surprising given the Government's inaction".
He suggested: “Every single day more people are presenting as homeless. Home repossessions, vacant possession of buy-to-let properties, spiralling rents and family breakdown are the key reasons.
“It is also deeply disappointing to see the Minister delay the release of the September figures and then quietly post them on the Department's website late in the evening when the country's media is focused on the Brexit Forum. This smacks of trying to brush this bad news under the carpet," he added.