The RAF and Royal Navy are under pressure to cut links with the sultan of Brunei amid a global backlash against his country’s decision to introduce death by stoning as punishment for homosexuality.

The calls came after crowds protesting against the country’s new draconian penal code surged through barriers outside the Brunei-owned Dorchester Hotel yesterday afternoon, forcing the police to stand in front of its doors.

More than 100 people, many bearing a mixture of rainbow flags, banners and placards, chanted “shame on you” outside the luxury hotel in Park Lane.

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The protest was led by gay-rights campaigner Peter Tatchell, who said: “The sultan is copying the barbaric punishments by Isis in Syria and Iraq; enacting death by stoning for people found guilty of homosexuality, adultery and insulting the prophet Muhammad.

“He is comparable to the Isis fanatics who executed people for these so-called crimes during their murderous caliphate. Brunei should be isolated as a pariah state, just like Isis was.”

Celebrities including Sir Elton John, George Clooney and Ellen DeGeneres last week urged a boycott of Sultan Haji Hassanal Bolkiah’s hotel empire, which includes London’s Dorchester and 45 Park Lane.

The protest came amid calls for the sultan to be stripped of two honorary appointments awarded by the Queen: he is an air chief marshal in the RAF and an admiral of the Royal Navy.

“Brunei’s deplorable new laws are a breach of basic human rights and contrary to the values that should define British institutions,” said Stephen Evans, chief executive of the National Secular Society, which challenges religious privilege.

“Stripping the sultan of the honours they have bestowed upon him would send out the important message that they do not wish to be in any way associated with this sort of medieval barbarism.”

A spokeswoman for Buckingham Palace said: “Her Majesty acted on the advice of government in relation to these honorary appointments.”

A spokesman for the Cabinet Office said: “We do not comment on individual cases.”

The protests come after it emerged that defence secretary Gavin Williamson had asked Brunei for assurances that gay British troops in the state would not be affected by the new laws, and several leading universities signalled they were preparing to revoke the sultan’s honorary degrees.

Facebook Twitter Pinterest The sultan of Brunei at an event in Bandar Seri Begawan on 3 April. Photograph: STR/EPA

Oxford University, which awarded him an honorary degree in civil law, said on Saturday: “We will reconsider this decision through our established process in light of the information now available, as other British universities are doing.”

The sultan has also been given honorary degrees by the University of Aberdeen and King’s College London (KCL). A University of Aberdeen spokesperson said: “The honorary degrees committee has agreed that these anti-LGBT laws are totally counter to the university’s founding principles and values. Their recommendation now passes to our senate to consider, which we anticipate to happen next week.”

In a letter to Evans at the National Secular Society, Professor Edward Byrne, president and principal of KCL, said he shared the society’s concerns. He said he had asked the committee that bestows the titles to reconvene “in light of the issues you raise”.

Other universities have also taken steps to distance themselves. Both Bangor and Nottingham are listed as global partners on the website of the University of Brunei Darussalam, which has substantial links with the sultan. Nottingham said it had “asked the university to remove the information from its website”, while Bangor confirmed it had “already taken the decision not to renew a student exchange scheme”.

Evans said the UK’s armed forces now needed to follow the example of the universities. “Brunei’s deplorable new laws are a breach of human rights and contrary to the values that should define British institutions. Stripping the sultan of the honours they have bestowed upon him would send out the important message that they not wish to be in any way associated with this sort of medieval barbarism.”

In addition to homosexuality, the new penal code says extramarital sex, anal sex and abortion are to be punished by death by stoning. The death penalty will also be applied to other offences, including rape and certain forms of blasphemy. The punishment for lesbian sex will be 40 lashes.

Organisations including English National Ballet and the Make-A-Wish Foundation have cancelled events at the Dorchester hotel, the Guardian has reported. Companies including Deutsche Bank have banned staff from staying at Brunei-owned hotels.