Flat-sharing renters in London need to find more than £2,000 before they are able to move home, according to property listings company SpareRoom. The combination of deposit, first month's rent, letting-agent fees, and removal costs mean that on average, a renting Londoner needs £2,043 to move somewhere else in the city, said SpareRoom, citing a survey of its users. Across the whole of the UK, the average upfront costs for moving flat-sharers is £1,175.

More on London rents from IBTimes UK

A housing shortage in London has driven up house prices sharply in recent years, pushing more people into the city's private rented sector and forcing up rents.

Demand for housing is estimated to mean that 50,000 new homes are needed every year in London, but around half are actually being built. Sadiq Khan, mayor of London, has floated the idea of a 'London Living Rent' that indexes rent costs for new properties to local earnings as a means of keeping rents affordable.

"The high cost of moving means that flexibility – one of the main benefits of flat-sharing – is starting to suffer," said Matt Hutchinson, director of SpareRoom. "Six-week deposits are becoming common, especially in London, and as deposits are linked to rents they're getting more expensive across the board as rents rise.

"With renters having to find a new deposit before they get their old one back, many simply can't afford to move. That can mean missing out on employment opportunities or having to put up with rent increases. One option to avoid longer deposits and high fees, or even to avoid fees altogether, is to deal direct with the landlord or rent a room from a homeowner looking for a lodger."