Simon Community's CEO Sam McGuinness has said the people who started the organisation 50 years ago would never have thought that it would still be needed today.
He was speaking at the launch of the Simon House of Light Festival at the Powerscourt Townhouse Centre in Dublin, where he was joined by actor and Peaky Blinders star Cillian Murphy to turn on the lights.
For his part, Mr Murphy said that homelessness is not a problem that needs to exist, adding: "If there's enough imagination, if there's enough resources, if people actively engage with it, I think hopefully it's something we can solve".
The Simon House of Light will run from 5pm to 10pm on Friday and Saturday (6-7 December) projecting an animated Christmas story onto the facade of Powerscourt Townhouse Centre on South William Street in Dublin city centre.
There will also be musical performances.
Simon Community say the event aims to bring people together to highlight the issue of homelessness.
Donations will be welcomed on-site throughout the festival.
Shining a light on homelessness: Cillian Murphy was speaking this evening at the launch of the Simon House of Light festival in Dublin. He said homelessness is not a problem that needs to exist. pic.twitter.com/nHq73fj4Ne— RTÉ News (@rtenews) December 5, 2019
Separately, several hundred people marched through Dublin city centre today to protest against rising homelessness.
Earlier, the Simon Communities' annual report, released today, showed that 16,776 people used its services in 2018.
This included 2,834 families with 5,331 children, which was up from 13,304 people in 2018.
The report also showed a 79.5% increase in the number of people accessing the homelessness and housing charity's emergency accommodation services.
National Spokesperson for the Simon Communities Wayne Stanley said this week's latest homeless figures showed record levels of people forced to access emergency accommodation in October.
He said more than 10,500 men, women and children will now enter the new year in that situation.
Several hundred people marched through Dublin city centre today to protest against rising homelessness. Earlier, one of the country's biggest housing charities said it assisted just under 16,800 people last year. Some 5,300 of those were children. pic.twitter.com/vNj2xBAkIb— RTÉ News (@rtenews) December 5, 2019
He said: "We have seen levels of rural and long-term homelessness increasing, along with instances of 'hidden homelessness' and those forced to stay with family or friends.
"We are all aware that the main driver of homelessness is a critical lack of secure affordable accommodation, and this is something that needs to be addressed by Government."
He added that it was vital that the current upward trend in homelessness does not become normalised.
Speaking on RTÉ's Morning Ireland, Mr Stanley said the charity has expanded its emergency services to help homeless people affected by trauma.
"Another place where we are putting effort into is to see how we can work with people who have had incidences of trauma whether it is a family breakdown, addiction. There is never one thing that causes homelessness. It is usually an accumulation of things."