Rents in London have hit double those for the rest of the country for the first time ever in the Homelet Rental Index.
Tenants are paying an average £1,412 a month in the capital, compared with £694 elsewhere, according to the firm’s latest data.
The study also revealed buy to let rents have shot up by 6.3% in the past year – to a nationwide average of £862 a month.
The firm argues that rents in the capital and surrounding counties are rising so far, they are almost becoming unaffordable for tenants on average wages.
In London, rents average rents are 2.23 times average incomes.
Although national rents show an average increase of 6.3%, those in London have soared by more than 11%, according to the report.
However, rents in the North East and Scotland returned slight falls.
Spokesman Martin Totty said: “The private rental sector continues to show strong growth with rental values increasing year on year across the country, with little exception. Although average incomes have also been rising, there are parts of the country where we are seeing affordability getting tighter.
“As a rule of thumb, for a rental property to be affordable, a tenant’s gross income must be at least two and a half times his or her annual rent. Our data shows that rents in London have pushed beyond that boundary, with the South East and South West of England close behind.”
Meanwhile, the latest rental data published by the government agency The Office of National Statistics for June 2014 shows rents only increased by 1% in the year, although the highest growth was in London, which returned a 1.4% rise.
Different indices can return varying results for a number of reasons, including sample size, demographic information.
For example, the Homelet index is based on a sample of rents agreed on tenants referenced by the company for lettings agents and landlords.