More than 10 million people in the UK have access to accommodation from private landlords, according to data compiled by the Shelter charity.
But despite this, many remain at risk of homelessness.
The charity has been investigating the issue and found the figures were based on figures provided by private landlords.
This means that the figures may be low, because they do not take into account people who rent privately.
For example, the charity does not take people with housing benefit into account in calculating the number of people on housing benefit, or how many people they can support, and it also ignores people on unemployment benefits.
But Shelter also found the data was not collected for all landlords, and that the average number of properties in England and Wales owned by private tenants was slightly less than the national average.
And the number renting from private renters is higher than the number that are owned by housing associations.
It comes as the Government continues to work to get more private landlords into the sector, with a £20m funding commitment from the Department for Communities and Local Government.
The Government will also be investing £1m in the sector by 2020 to increase the number and diversity of landlords who will be able to accept private tenants.
However, Shelter said that while the data provided by the private sector was good, it did not account for the large number of landlords that have taken advantage of the scheme, or the people who have been forced into homelessness.
Shelter has launched an investigation into how landlords in the private rental sector are managing their business and said the numbers may be underestimated.
The organisation has launched a report on the issue, which will be published this week.