George Clooney has called for a boycott of nine luxury hotels, including the Dorchester on Park Lane in London, because of their links to Brunei, which plans to impose death by stoning as a punishment for gay sex and adultery from next week.

“Let that sink in. In the onslaught of news where we see the world backsliding into authoritarianism this stands alone,” the film star and activist wrote in an opinion piece for Deadline.

In a novel form of political activism aimed at the global elite, he called for the public to join him in immediately boycotting the hotels operated by the Dorchester Collection luxury chain: three in the UK, two in the US, two in France and two in Italy.

The Dorchester Collection is owned by the Brunei Investment Agency, an arm of Brunei’s ministry of finance. The British hotels are the Dorchester and 45 Park Lane in London, and Coworth Park in Ascot, Berkshire. Other hotels in the group include the the Beverly Hills hotel and Hotel Bel-Air in Los Angeles.

“Every single time we stay at, or take meetings at or dine at any of these nine hotels we are putting money directly into the pockets of men who choose to stone and whip to death their own citizens for being gay or accused of adultery,” Clooney said.

“Are we really going to help pay for these human rights violations? Are we really going to help fund the murder of innocent citizens?”

Saying he had no complaint against those who worked in the hotels, Clooney added: “I’ve learned over years of dealing with murderous regimes that you can’t shame them. But you can shame the banks, the financiers and the institutions that do business with them and choose to look the other way.”

Clooney wrote that a previous boycott of the chain’s Californian hotels had been “effective to a point … But like all good intentions when the white heat of outrage moves on to the hundred other reasons to be outraged, the focus dies down and slowly these hotels get back to the business of business”.

George Clooney: ‘Are we really going to help pay for these human rights violations?’ Photograph: Andrew Milligan/PA

The tiny south-east Asian kingdom of Brunei, which has adopted a more conservative form of Islam in recent years, first announced in 2013 its intention to introduce sharia law, the Islamic legal system that imposes strict corporal punishments.

The draconian penal code, due to be implemented from 3 April, is a directive of the sultan, Hassanal Bolkiah, one of the world’s richest leaders with a personal wealth of about $20bn (£15bn). The sultan, who has held the throne since 1967, has described the planned implementation of the penal code as “a great achievement”.

The plan was condemned by the UK Foreign Office and the international development secretary, Penny Mordaunt. A battalion of British troops is stationed in Brunei, and the oil-rich state has been targeted by the UK for a new free trade deal after Brexit.

“Corporal and capital punishment goes against our national values and has been banned in the United Kingdom for decades. The Minister for Asia and High Commissioner have raised their concerns in person, and we have updated the travel advice to warn British citizens of the new local laws in Brunei,” the Foreign Office said.

“No one should face the death penalty because of who they love,” Mordaunt tweeted. “Brunei’s decision is barbaric and the UK stands with the LGBT+ community and those who defend their rights. LGBT+ rights are human rights.”

The Beverly Hills hotel communications director, Brittany Williams, said: “Dorchester Collection’s code (emphasises) equality, respect and integrity in all areas of our operation, and strongly values people and cultural diversity among our guests and employees. Inclusion and diversity remain core beliefs as we do not tolerate any form of discrimination.”