Labour’s announcement that it will bring in an annual mansion tax on all homes worth £2m or more to raise money for the NHS has been labelled a “political stunt’.

The British Property Federation was among the many critics of the move – described by Knight Frank as purely political. Other critics have said that the tax will pull in property rich but income poor people who have lived in homes for many years. Their homes have risen in value, but say pundits, these owners would be utterly unable to pay the tax.

Head of research at Knight Frank, Liam Bailey, said that one in ten homes whose owners would have to pay the tax are in London – but have just one or two bedrooms.

He said another 17% have three bedrooms, and that just 1% would be considered ‘mansions’ in the traditional sense, with ten or more bedrooms.

According to Bailey, there are about 110,000 homes in the UK valued at £2m or more.

Almost all – about 86.4% – are in London and the south east.

Bailey said: “It’s quite clear the objective of this is political.”

Knight Frank’s estimate of the number of £2m-plus homes is at the top end of the scale, with Hometrack estimating about 58,500, Savills about 97,000, and Zoopla 108,000.

According to Zoopla 96% of the burden of Labour’s mansion tax would fall on home owners in London and the south east.

Zoopla reckons over 85,000 home owners in London would be caught by the tax, and over 14,000 in the south east. After that, the numbers drop away sharply with, for instance, just 168 home owners caught by the tax in Yorkshire and the Humber, and 87 property owners in Wales.

It estimates that the tax would cost an average of £15,000 a year.

Lawrence Hall, of Zoopla, said: “It is somewhat misleading to call it a mansion tax when many three bed family homes in London and the south east would find themselves caught by it.”

The Labour party estimate that the mansion tax will bring in £1.2bn a year to fund the NHS.

Yesterday evening, on Radio 4, shadow health secretary Andy Burnham said the mansion tax would be introduced immediately on a Labour victory, with funds quickly going into the NHS.

However, he appeared stuck for an answer when asked how the homes would be valued, saying only that there already was an internal government valuations service.