The pressure group Generation Rent - often identified with highlighting issues concerning young tenants - is now warning of a massive rise in pensioners who rent privately in the next two decades.
In a report the group has co-authored with David Adler of Oxford University, Generation Rent says it forecasts that by 2035 nearly one million households of retirement age will be renting from a private landlord.
Currently the figure is 370,000 "so this projection suggests these numbers will nearly treble" says the group, which bases its data on findings from the English Housing Survey.
The forecast assumes continuation of current home buying rates among the over-45s, and no increase in the availability of social housing.
"Most will rely on housing benefit to keep a roof over their heads. An extra 600,000 housing benefit claimants would cost the state £3.46 billion per year at today's price" it says.
As the tenant population ages, demands for reform of the private rental sector will increase, the group anticipates.
"Faced with a ticking fiscal timebomb, the answer for politicians is not further cuts to housing benefit, because that will only further immiserate people who have nowhere else to turn. Indeed, it will become electorally impossible to ignore their plight" claims the organisation.
It calls for "a transformation of the private rental market into a professional provider of long term homes."