By Sharon Abratique

HONG KONG (Reuters) -Hong Kong’s legislature approved the biggest overhaul of its political system in the quarter century since British rule on Thursday, in a decisive step to assert Beijing’s authority over the autonomous city.

The move was quickly denounced by the United States, which accused China of undermining Hong Kong’s democratic institutions and said decreasing electoral representation of residents of the territory would not foster long-term stability.

The changes will reduce the proportion of seats in the legislature that are filled by direct elections from half to less than a quarter. A new body will vet candidates and bar those deemed insufficiently patriotic towards China from standing.

“These 600-or-so pages of the legislation come down to just a few words: patriots ruling Hong Kong,” said Peter Shiu, a pro-Beijing lawmaker.

Most of the changes were announced by China in March, though Hong Kong authorities later contributed further details, such as redrawing constituency boundaries and criminalizing calls for ballots to be left blank.

The measures were passed with 40 votes in favor and two against. The pro-Beijing government has faced no opposition in the legislature since last year, when China disqualified some pro-democracy lawmakers and others resigned in protest.

Chinese authorities have said the electoral shake-up is aimed at getting rid of “loopholes and deficiencies” that threatened national security during anti-government unrest in 2019 and ensure only “patriots” run the city.

The legislature will increase in size to 90 seats from 70. The number of seats filled by direct election will decrease to 20 from 35. Forty seats will be filled by an election committee, which is also responsible for choosing the chief executive.

The new vetting committee empowered to disqualify candidates will work with national security authorities to ensure those standing are loyal to Beijing.

In a statement, U.S. Secretary of State Antony Blinken accused China of continuing to undermine democratic institutions in Hong Kong and called on Beijing and Hong Kong authorities to release and drop charges against everyone charged under the national security law.

Blinken said altering the composition of the legislature “severely constrains people in Hong Kong from meaningfully participating in their own governance and having their voices heard.”

“Decreasing Hong Kong  residents’ electoral representation will  not  foster long-term political and social stability for Hong Kong,” he added.

Elections for the election committee are set for Sept. 19, and for the legislature three months later. The committee will choose a chief executive on March 27, 2022.

Chief executive Carrie Lam has not made clear whether she will seek re-election. In 2019 she faced the largest and most violent anti-government protests since the handover from British rule in 1997, after proposing a bill to allow extraditions to mainland China.

China had promised universal suffrage as an ultimate goal for Hong Kong in its mini-constitution, the Basic Law, which also states the city has wide-ranging autonomy from Beijing.

Democracy campaigners and Western countries say the political overhaul moves the city in the opposite direction, leaving the democratic opposition with the most limited space it has had since the handover.

Since China imposed a national security law in 2020 to criminalize what it considers subversion, secessionism, terrorism or collusion with foreign forces, most pro-democracy activists and politicians have found themselves ensnared by it or arrested for other reasons.

(Writing by Marius Zaharia; additional reporting by Daphne Psaledakis and David Brunnstrom in Washington; Editing by Peter Graff and Lisa Shumaker)