Many people now share ownership of a property or live as lodgers, suggest the Resolution Foundation think tank, meaning an official estimate of a 64 per cent home ownership rate may be overestimated.
The Resolution Foundation, which focuses on policy concerning those on middle to low incomes, that it could be as few as 51 per cent of families or individuals who own a home in Britain.
Instead of focusing on the proportion of properties owned by the occupier, as the official Office for National Statistics does, the think tank looked at the proportion of people who own houses.
"All these real-life situations have largely been missed out of the tenure story to date," read an explanation on the group's website.
"So what happens if we switch our attention from households to families - by which we mean here a single adult or a couple - along with any dependent children? A different picture of how we are housed emerges."
ONS figures failed to account for the 5.8m families or individuals who lived with the home owner in their property, therefore not representing young adults who returned to live with their parents, according to the Resolution Foundation.
Instead, a single adult should be considered as their own family unit meaning that while the ONS regards a house rented by five adults as one single rented households, the Resolution Foundation believe this would be better interpreted as five single adults who rent.
The think tank is calling for "the other half" of the population who rent to receive more attention from policymakers and politicians.
While millennials are particularly well-represented amongst renters due to high house prices, the Resolution Foundations stresses that it is not limited to that generation, citing a rise from one in 20 families headed by a 35 to 44 year-old living in a rented property in 1992 to one in five in 2015.
"Living in the private rented sector isn’t just a millennial problem then – it is taking hold across people’s life stages and merits wider examination," reads the think tank's website.