Research by Savills suggests that the mansion tax could effectively decide which major party wins some key London marginal constituencies on May 7 - and, given the closeness of opinion polls, these seats could decide the whole election.
Savills data, quoted in London's Evening Standard, shows that a quarter of sales of London homes worth more than £2 million since 2011 have been in Labour-held seats. Lucian Cook, the agency's director of residential research, says: Our analysis shows that the mansion tax could be a significant issue for the electorate in a number of key constituencies in London.
The proposed tax may not influence only those with homes valued at over £2m - at which point the tax will start - but owners with properties currently valued at around £1.5m who may fear that appreciation will take their property above the threshold.
The Standard says some of the marginal seats in the capital include Hampstead & Kilburn - currently Labour held but a Tory target seat - as well as Brentford & Isleworth and Battersea, which are Labour targets not currently held by the party.
The paper says Conservatives believe up to 2,000 votes could be swayed in some constituencies by the tax, although Labour insists the issue is not a major one for most voters.
In recent months both Savills and Knight Frank have prominently highlighted the possible effects of a mansion tax, and have suggested possible alternative means of property-related revenue raising, such as reformed council tax.