Three quarters of London properties which would fall into the so-called “mansion tax” bracket are flats or terraced houses, according to Knight Frank figures.

The property consultants analysed sales data to see what type of “mansions” would fall into the £2m plus category Labour leader Ed Miliband would target if his party came to power.

Knight Frank said London – and in particular the prime areas of Westminster and Kensington & Chelsea – would be hit harder than other parts of the country by the tax. The two boroughs alone account for 46 per cent of the £2m-plus properties in England and Wales, and 26 per cent of properties eligible for the mansion tax in England and Wales are flats in those two areas.

Across Greater London, 38% of all of the taxable properties are flats while only 14% are detached. Terraced houses are the second-largest group falling into the category, at 36%, while semi-detached properties make up the remaining 12%t.