The proposed "mansion tax" on homes worth in excess of £2 million might be popular with voters but some campaigners say the idea is unfair and contrary to "humanitarian" values.
According to Zoopla, the average price of a detached house in Hampstead is almost £5 million.
The Stop the Mansion Tax group argues that although residents of expensive London properties are asset-rich, some are cash-poor and could be forced to move out due to extra payments.
Another campaigner quoted by the paper, who lives in Hammersmith in west London, said the tax may force him to shut down the art gallery in his house. He said:
For me it would mean the closing of my business, the selling of my house and a complete upheaval of everything that I hold dear.
The person I'm most concerned about is my mother who lives in a house which is probably worth £4 million, which my father bought in 1960. She would have to move and at the age of 77 it would be extremely traumatic for her.
The mansion tax is controversial even within the party that suggested it. Several leading Labour figures signalled their opposition, including London MP Tessa Jowell, who said:
But let's stop calling it a 'mansion tax', these are not mansions, these are family homes that have accrued in value.
When people think of mansions they think of great big Scottish estates, or Cotswold estates, or whatever, this is a feature of the London housing market. These are people who do not think of their home as this fast appreciating capital estate but as their family home. ...
The reason I've been speaking out against this is that I did not want a situation to arise where these people felt helpless and anxious in ways that meant the only option open to them was to sell their homes.
Shadow chancellor Ed Balls sought to calm opponents' fears over the scheme in an article this week in London's Evening Standard.
He said people earning less than £42,000 a year would be able to defer the payments – equivalent to about £250 a month, the same as the top rate of council tax – until they sell the property.