Property in Westminster, Camden and Haringey has a combined value of just over £243 billion, more than the GDP of Denmark, the 35th largest economy in the world.

Westminster property accounts for almost half this figure, with a total value in 2014 of £120.4 billion, a year on year increase of £18 billion (17 per cent).

Research by estate agent Savills also found that the value of property in Camden increased 23.3 pc between 2013 and 2014 and is now worth £71.4 billion, while the total value of Haringey property is £51 billion.

This news comes as the main political parties have all stated their intention to levy some kind of tax on property, with the bulk of the money raised coming from London.

Revised Stamp Duty charges, which came into effect in December, are already raising significant revenue from the capital, while Labour have gained headlines with their proposed mansion tax on properties over £2 million.

Tom Wrigglesworth, sales manager at Brian Lack in St John’s Wood, said: “I think if a mansion tax is implemented, people looking around the £2 million mark will be hesitant to part with the extra money, so there’ll be a higher demand for homes just below the threshold, which will lead to a lot more competition in a bracket usually reserved in this area for families buying three-bedroom flats.

“I don’t think it will make much difference above the £10 million mark. For a lot of people from overseas, who are buying as investments, the extra cash demanded from a mansion tax would be pocket change. I don’t think they’d be deterred.”

The total value of stock in the private rented sector in the UK passed the £1 trillion mark in 2014, as restraints on mortgage lending restricted the availability of credit.

The number homes owned with a mortgage fell by 800,000 in the past five years, while the number of private rented homes increased by 1.2 million in the same period.

Paul Dimoldenberg, leader of the Labour Group, Westminster City Council, said: “The huge increase in property prices is making it increasingly difficult, if not impossible, for even people with decent salaries to live locally.

“For people on low or moderate incomes the situation is dire as they are being forced to commute long distances or pay very high rents to live in very average rented accommodation.

“We need more social housing to be built in Westminster and the rest of central London to cater for those on low incomes and to take the pressure off the private rented market.”