Biting cold weather stirs compassion for those forced to sleep rough, however shelter organisers said the dramatic increase was a warning to the ACT Government that current services were not catering to the city's most vulnerable.

Safe Shelter Coordinator, Richard Griffiths, said he and volunteers had seen many of the same faces fronting up at inner city Canberra Church Halls - an indication there were roadblocks for those seeking more permanent accommodation.

Mr Griffiths said extreme cold weather and shelter operating five nights, instead of three nights per week, were both factors, but but weren't a reasonable explanation for the huge spike.

"We've gone from three nights to five nights and that should logically mean an increase of two thirds, 67 per cent, but instead of that we have an increase of over 600 per cent," he said.

"We have gone from 24 guest nights in the first 10 weeks of winter last year, to 160 guest nights in the same period this year."

Safe Shelter suspects much of the increase is associated with the closure of public housing along Northbourne Avenue and the Allawah and Bega Flats.

While registered tenants may have been re-located, their guests, couch-surfers and those who might have been sheltering in laundries, stairwells, etc in those buildings would now be seeking alternative shelter.

"The figures suggest these people have always been there, in the public housing complexes, but they haven't been counted so their needs have not been met," Mr Griffiths said.

Groups of the same people have been staying for three and four weeks with Safe Shelter at various inner city church halls.

Mr Griffith said Safe Shelter was not always full but only had capacity to cater for eight to nine guests per night.

After that, shelter volunteers could offer a street swag to anyone they had to turn away.

"It is not a solution for a city," he said. "We don't have any permanency. We are open form 7pm to 7am. Guests have to front up each day. It really is emergency shelter. Sleep on the floor, you are warm, you're safe," he said.

Accommodation services that offered more than 12-hour stays for homeless men such as Samartian House were often at capacity.

Australian Bureau of Statistics said new national homelessness estimates derived from the 2016 Census may not be released until early 2018.

Mr Griffiths urged the ACT Government to take action now and re-assess the level of need in the community in light of this evidence that pointed to people falling through the gaps as a result of recent public housing closures.