Shelter Scotland said £200m would pay for 10,000 new homes for rent
Shelter Scotland has estimated an extra £200m a year is needed to tackle homelessness and poor housing.
The charity urged the Scottish Government to make affordable homes a priority in its forthcoming budget.
Director Graeme Brown said the money would help build 10,000 affordable homes to rent each year.
The Scottish Government said affordable housing was being built at a record rate, and more than £1.5bn would be spent over three years.
Shelter made the call for extra funding as ministers and MSPs returned to Holyrood after the summer break.
Mr Brown said: "In the history of the Scottish Parliament there has never been a more pressing need for investment in affordable homes to rent.
"This budget will determine how Scotland delivers its historic commitment to end homelessness by 2012.
"With the eyes of the world upon us we cannot afford to fail."
Shelter said a recent rise in the number of affordable homes being built was offset by properties being sold under right to buy legislation.
The call for additional funding was backed by Jacqui Watt, chief executive of the Scottish Federation of Housing Associations.
She said: "Due to money being brought forward to be spent this year, housing associations are seeing gaps opening up in their housing budgets for future years."
A spokesman for the Scottish Government said it was "pulling out all the stops" to increase the supply of affordable homes.
"We will approve grants for a record breaking 8,100 affordable homes this year, backed by £644m" he said.
"We are investing £50m to reverse decades of decline in council house building."