Tax rises on high-value properties, along with the prospect of a "mansion tax" and the uncertainty caused by a looming general election, have made homes that are worth more than £2 million ($3.24 million) much harder to sell, according to research for the Financial Times.

More than half of all properties in London's most expensive central areas have been withdrawn unsold in the six months to the end of June, the research by the property data company Lonres and analysts Dataloft shows.