In Kensington and Chelsea average annual rents totalled £36,520 per year – higher than average local incomes of £34,157, according to Paragon.
Westminster was found to be second least affordable with rent costing 81 per cent of local annual salaries on average followed by Hammersmith and Fulham with rent accounting for 61 per cent of salary.
Tenants in the capital often spread rental costs with others, resulting in London having the highest proportion of UK renters who share a property with people outside of their family.
Copeland, Ribble Valley and Staffordshire Moorlands were the most affordable places to privately rent in England last year.
Renting a property in Copeland, Cumbria, costs £5,236 a year, after taking local average salaries into account, rent accounts for 10.5 per cent of average earnings.
Across England, the average salary of £30,264 equated to 32 per cent of the average rent.
Affordability also correlates with property size. Renting an average four-bed home in England costs 60 per cent of salary, a three-bed 41 per cent, followed by properties with two bedrooms at 33 per cent.
Richard Rowntree, Paragon Bank managing director of mortgages (pictured), said: “Our rental affordability index shows considerable variation in how affordable privately rented homes are. A key influence on this is where properties are located with a general trend for more affordable housing being found in the north of England.
“The lower purchase prices for homes in regions such as Yorkshire and The Humber means that investors can keep rent prices relatively low while still covering their overheads.
“It’s important to acknowledge, however, that there is a limit to this, and the current economic conditions mean that it is becoming more expensive to manage a lettings business. Alongside supply of properties that is exceeded by demand, this is placing pressure on rents.
“The government and industry must work together to facilitate investment that will boost the number of homes available to rent, giving tenants more choice and helping to regulate rental costs.”