A New York City housing board has approved a key pledge made by Mayor Zohran Mamdani to freeze rents for about one million regulated apartments.

The result of the vote on Thursday was greeted with cheers and whistles from hundreds of people in Manhattan as the Rent Guidelines Board (RGB) approved a freeze on both one and two year leases.

Mamdani said in a statement that it was a "historic victory for New York City tenants".

The board voted in favour of the policy 7-1, hours after the public resignation of one of its members Christina Smyth, who accused the panel of bias and of "knowingly disregarding its own evidence" that landlords face spiking operating costs.

Smyth was one of three members appointed by former New York City Mayor Eric Adams. Mamdani appointed the other six members after taking office this year.

Smyth, one of two landlord representatives on the board, said the outcome had been predetermined by the mayor.

"The rebuilt board was required to deliver a rent freeze," she said. "Everything since has been theater," she said in a statement.

Chair of the board, Chantella Mitchell, said the board's members served with independence and integrity.

In a statement concerning the rent freeze, she said "comprehensive data before the board this year reflect an economic environment in which most tenants in rent-stabilised housing struggle to meet basic affordability thresholds as housing costs continue to rise".

Rent-stabilised buildings will be eligible for the rent freeze across all five of the city's boroughs between October 2026 and September 2027. They include buildings ranging from high-rise luxury apartments to affordable subsidised units.

Tenants had argued in public hearings held ahead of the vote that incomes were not keeping up with inflation and that past rent increases hadn't gone towards building repairs or improvements.

But groups representing landlords warned that it would be more difficult to keep up with rising taxes, utilities and repairs as a result of the freeze, leading to worse conditions for renters.

"Older rent-stabilized buildings are already struggling under rising operating costs, yet the Board chose to disregard those realities," said James Whelan, president of the Real Estate Board of New York.

"This decision will mean less investment in maintenance and repairs, accelerating the deterioration of the housing stock that millions of New Yorkers call home," he said.

During Mamdani's campaign for mayor late last year, his election pledges centred on cost-of-living issues, with the rent freeze being one of the core promises.

Changing the make-up of the board was also among the democratic socialist mayor's pledges.

In a video from January 2025, Mamdani said the terms for eight of Adams' nine RGB board appointees were up and he would replace them if he became mayor, promising he would be "only appointing those who understand that landlords are doing just fine".

A preliminary vote in May by the rent guidelines panel had endorsed Mamdani's plan to effectively freeze rents for nearly one million New York apartments.

Rent freezes have been enforced three times before between 2015 and 2021 under former New York Mayor Bill de Blasio, but only for one-year leases.

The rent freeze win for Mamdani adds to the successful election of a trio of left-wing congressional candidates backed by the mayor on Wednesday.

Two of the candidates Mamdani endorsed, New York City Comptroller Brad Lander and community activist Darializa Avila Chevalier, unseated incumbent Democratic congressmen.

In the third race, state assemblywoman Claire Valdez beat an opponent who had the backing of much of New York City's Democratic establishment.