An expanded mansion tax proposed by the UK government is expected to disproportionately affect Labour-held constituencies in London, according to recent data analysis. Chancellor John Healey is reportedly considering lowering the tax threshold from £2 million to £1.5 million, a move that would bring an additional 112,000 homes into the tax net ahead of its planned introduction in April 2028.

The mansion tax would require owners of properties valued above the threshold to pay an annual levy ranging from £2,500 to £7,500, depending on their home’s value. Initially set to target homes worth more than £2 million—estimated at around 165,000 properties across the country—the proposed reduction in the threshold to £1.5 million would increase the number of affected homes to approximately 277,000.

Analysis by the estate agency Hamptons, using Land Registry data, reveals that nine of the ten constituencies most heavily impacted by this change are represented by Labour MPs. In London specifically, areas with higher property values and a greater concentration of Labour representation would face the greatest burden. Kensington & Bayswater, held by Labour, would see about 3,000 additional homeowners subjected to the tax under the lower threshold, with half of the homes in the constituency exceeding £1.5 million. Hampstead & Highgate, another Labour seat, ranks second with 40 percent of homes above that value, while Chelsea & Fulham follows closely with 33 percent. The only non-Labour constituency in the top ten is Richmond Park, represented by a Liberal Democrat MP.

Overall, among the top 20 constituencies most affected by the expanded tax, 15 are Labour-held, four are Liberal Democrat-held, and one is Islington North, where Jeremy Corbyn serves as an independent MP.

Several Labour MPs have expressed concerns about the revised threshold, describing the tax as being "anti-London" due to its heavier impact on London boroughs, where house prices tend to be significantly higher than in other parts of the UK.

The Treasury defended the plans, emphasizing the need for reform to address disparities in the current council tax system. A spokesperson stated that the changes aim to rectify a longstanding imbalance where lower-valued properties in towns such as Darlington or Blackpool can pay more council tax than multimillion-pound homes in affluent areas like Mayfair.

The proposed mansion tax is part of broader efforts to increase revenue by targeting wealthier homeowners, although the debate continues over its fairness and potential political ramifications, particularly for Labour MPs representing high-value London constituencies.