Affordability pressures in the private rental sector mean that far fewer tenants are now renting properties with spare bedrooms according to Countrywide.
It says only 35 per cent of tenants taking up tenancies this year have rented a property with a spare bedroom; back in 2010 the figure was 59 per cent.
London has seen the largest manifestation of this trend: new tenants with a spare bedroom have fallen from 61 per cent in 2010 to 26 per cent today. Other large 'rental' cities - notably Oxford, Cambridge and Bristol - have witnessed a similar trend.
The cost of renting an extra bedroom is £295 per month - some 14 per cent more than five years ago, says the agency.
"Sacrificing extra bedrooms and sharing has helped renters to absorb higher prices. But those living in the south [of England] are close to a point where there's not much room to squeeze, meaning rental growth is likely to be capped by tenants' incomes for some time" warns Countrywide's director of research, Johnny Morris.
The agency says rental growth continues to slow across Britain, with annual rent increases nationally being just one per cent.