In three years, the number of people seeking help from Mission Australia's homelessness services has surged by 26 per cent.

But only one in three people were found a secure, long-term home, because of a "chronic and significant lack of social and affordable housing".

The findings were released by the charity in its first homelessness impact report on May 23.

Mission Australia chief executive Sharon Callister told ACM the report confirmed fears that the crisis is "the worst it's ever been".

"There are no other words for it except alarming," she said.

"If people were coming to us while they were still in housing, but very much at risk [of homelessness], there was a 94 per cent chance we could help them maintain long-term housing.

"If you compare that to people who came to us who were already homeless, we only had a one in three chance of getting them a permanent home."

Mission Australia provides support nationwide but the majority of its homelessness services are based in NSW.

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"If you asked St Vincent de Paul or the Salvos or any other organisation right around the country I'm pretty sure they'd come back with the same answer - this is not a city issue and it is not a particular state issue, it is right across the board and it's a real emergency," Ms Callister said.

Mission Australia is calling for more investment in homelessness prevention and support services. It wants an estimated one million new social and affordable homes to be built in the next 20 years.

Sydney man Stephen Coffey reached out to Mission Australia in late 2021.

The former builder left his family home after a marriage breakdown and started using heroin.

"I became a heroin addict and that slowly sucked everything I had until I had nothing except a car to sleep in," he said.

"Some two, three years before I went [to Mission Australia] I had actually finally dried out from drugs but when you're homeless, when you've got nothing, it's hard to come up with the deposits and payments for housing."

Mr Coffey was taken into transitional accommodation at Mission Australia's Ebbs House for about a month before a permanent home was found for him.

The 72-year-old said he had tried to find a home through an affordable housing service before "but was getting nowhere".

"It was Mission Australia that opened the door," he said.

And now he says he is "going fantastic".

"I look after myself which I'm capable of doing and while I'm still capable I go up [to Ebbs House] and I do little jobs around the place to help them out and pay back in the spirit of mankind."

Mr Coffey urged people to have "empathy and compassion" for those experiencing homelessness.

"I know that no matter how high up the ladder you are, things can change and before you know it, you could be on that doorstep," he said.

Since 2020, nearly 10,000 people experiencing homelessness and a further 8000 who were at risk have been supported by Mission Australia.

Most people seeking help were relying on income support payments; not sufficient amid the cost of living and housing crisis.

But the charity was also being approached by a growing number of working people who couldn't afford rising rents.

"We have had probably a decade of stagnant wage growth, we've had the COVID pandemic and we have had skyrocketing prices in terms of rental and housing," Ms Callister said.

"And if you put all of that together it's almost a perfect storm."

She said a change in mindset was needed about what homelessness looked like.

"The largest growing group of people [seeking help] are women with young children fleeing family and domestic violence," she said.

"And after that it's women over 55 years of age."

Without an urgent and significant boost in stocks of social and affordable housing, Ms Callister said homelessness would not be eliminated.