Mayor Andy Burnham has unveiled a £7.5 billion homes tax aimed at London.
The levy targets newly built homes and would be added to property costs.
Buyers are increasingly asking for a "Burnham discount" as they factor the tax into offers.
Business groups warn this levy could scare investors away from the capital.
Housing advocates maintain the revenue could alleviate the city’s shortage of affordable homes.
Observers note the proposal may transform regional economic policies and affect how middle‑earners plan home purchases.