The number of homeless is expected to rise this year
Homeless people need more help to deal with mental health problems, leading charities are warning.
Experts have already predicted that the recession could lead to a rise in homeless people.
And now Crisis and St Mungo's have called for improved access to specialist services because of the high rates of problems being reported.
Research shows that a third of people in hostels have severe mental health problems such as personality disorders.
Once other conditions, including depression and anxiety, are taken into account as many as eight in 10 are affected.
But the charities, which run homelessness services including hostels, said most are given no help.
One of the key reasons why homeless people struggle to access services when they want to is that they are often not registered with a local GP.
The campaigners called for mental health specialists to run outreach clinics in hostels as well as greater access to drop-in centres.
They are now planning to hold discussions over the next 10 weeks with other homeless services, NHS experts and social services to see what can be achieved, before publishing a full report in the summer.
While the number of rough sleepers has been falling in recent years, there are still estimated to be about 800 people on the streets of the UK at any one time.
On top of that there are more than 40,000 people living temporarily in shelters and hostels.
And many believe these figures will rise in the coming months as people struggle to cope in the current financial climate.
St Mungo's chief executive Charles Fraser said: "These are often the individuals with the most intractable problems, who need the most determined help and it is reprehensible they are not getting it."
And Leslie Morphy, the head of Crisis, added: "The link between homelessness and mental health problems is well known.
"Yet, despite all the evidence, we still do not have the right services and support in place to address what is both such a common cause and consequence of homelessness."
But the Department of Health said funding for mental health services had been increasing and local health bosses were investing some of this into care for homeless people.
"Many trusts now have successful community outreach teams that work with hard to reach people such as the homeless."