Mansion tax: London would pay 90pc of £1.2bn bill

He said similar taxes applied in New York, Paris and Frankfurt.

The tax has provoked angry criticism from those in expensive areas, with suggestions that some people with low incomes or little ready savings would be forced to move.

Both Labour and the Lib Dems have faced criticims in the past for the alleged inaccuracy of their estimates of how much a mansion tax would raise. The Lib Dems reckoned it would bring in £1.7bn per year, while Labour put the figure higher at £2bn.

Knight Frank, the upmarket property group, estimated a far lower £1.3bn. This is closer to the Zoopla figure of £1.2bn.

Its estimates suggest 82,000 property owners would pay the tax, if implemented as proposed, resulting in an average yearly bill of £14,500 for those households affected.

Zoopla's Lawrence Hall said: “Homeowners in London and the South East already pay the lion’s share of UK property taxes with the stamp duty thresholds placing a heavy burden. Implementing an additional charge based on higher property values over an arbitrary threshold would only serve to further distort the market.”

The controversy is further escalated by the widening divide between London prices and those elsehwere, which has reached a new record .

Other recent data showed the total mortgage debt in just one part of London - the south western areas where postcodes begin "SW" - outweighs the toal mortgage debt in all of Wales.

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