Mayor Andy Burnham has unveiled a £7.5 billion homes tax aimed at London.
The levy targets fresh construction projects and would be tacked onto property costs.
Buyers are already asking for a "Burnham discount" as they factor the additional charge into offers.
Business groups warn the charge could discourage investors away from the capital.
Housing advocates maintain the revenue could alleviate the city’s shortage of affordable homes.
Observers observe the proposal may alter regional economic policies and impact how middle‑earners plan home purchases.