The Simon Communities of Ireland has said more than 13,000 people it assisted last year amounts to an increase of two thirds in two years.
They were seeking help to secure various housing support services including access to emergency accommodation.
Launching its annual report for 2017, Niamh Randall of Simon said that 2018 would be a record year for homelessness.
She said more than 81,000 people are facing Christmas with no secure place to call home.
Simon Communities will give a breakdown of the different services it provided last year - and how many people availed of them.
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The homeless charity's annual report shows that more than 13,300 people required its help in 2017.
Among them are more than 2,000 families and 3,800 children.
Simon Communities has also revealed that 1,218 people accessed its emergency accommodation services in the first six months of 2018.
That compares to 968 people for the whole of 2017.
Speaking on RTÉ's Morning Ireland, Ms Randall said: "What we saw from January to June 2018 was an increase in people accessing our emergency accommodation services, so that was about 1,200 people.
"We also saw 3,140 families. That figure was 2,006 for the whole of 2017. So what we are anticipating is that 2018 will be a record year, unfortunately".
Cork Simon provided support to just over 1,400 people in 2017 (1,403), an 18% increase on 2016.
While figures for 2018 have not been compiled, all the indications are that demand for the charity's services increased again this year.
For instance, there were 47 beds in the Cork Simon emergency shelter at Anderson's Quay this time last year.
A further 15 temporary emergency beds were added in the run-up to Christmas, to bring the bed complement to 62 until March.
However, those 15 temporary beds remained in place right through this year, and a further three emergency beds have been added to bring the total number of emergency beds at the Cork Simon shelter to 65.
Cork Simon also has a street outreach team, which provides a soup run and other assistance to rough sleepers and others on the margins in the city.
It also provides addiction support and other services.
It operates a number of flats around the city and has five high-support houses where shared accommodation is available to people moving from homelessness.
It also has a housing support team.
Meanwhile, the Minister of State for Housing and Urban Renewal said the Government has no plans to enshrine the right to housing into the Constitution.
Damien English said the move would not make much a of a difference to the current situation because as things stand his department is doing all it can to provide new homes.
He was responding to comments by the Simon Communities of Ireland today which repeated its call to include the right to housing into law.
Mr English said the Government is taking its responsibility very seriously, to ensure everyone has a home.
Additional reporting: Paschal Sheehy