England will need 934,388 additional properties available at sub-market rent if severe shortfalls between demand and supply are to be met, youth homelessness charity Centrepoint said.
Its research found that more than 137,500 properties are needed to meet demand from under-25s alone.
London has the overall largest shortfall at 186,333, followed by the East Midlands at 132,587 and Yorkshire and Humber at 128,478.
The study was the first to solely examine the number of units needed below market rents including council, housing association or private rented sector units accessible with housing benefit.
Although the report suggests that part of the solution has to be building more homes in both the private and rented sector, it also highlights that better use could be made of existing stock.
The research, which was carried out by the University of Cambridge on behalf of Centrepoint, also highlighted the growing shortfall in homelessness provision for young people. Thousands more units of supported accommodation - such as hostels - will be required by 2021 to house young people initially after they become homeless.
"Whilst it's vital that more affordable homes are built, there are also other ways of tackling the problem which don't come with a huge price tag. Local authorities must look at using powers they already have to tackle empty homes and engage further with the private sector, and nationally, Government has to review its cuts to housing benefit rates, which has left private rented properties out of reach in many areas of the country."
Housing Minister Mark Prisk said: "Four hundred and twenty thousand social homes were lost under the previous administration, but we are building 170,000 new affordable homes for rent and affordable home ownership by 2015, and are planning to accelerate the building rate from next year."