BEIJING--A former employee of the British Consulate in Hong Kong says he was detained and tortured by Chinese secret police trying to extract information about massive anti-government protests in the territory.

Simon Cheng said in an online statement and media interviews that he was hooded, beaten, deprived of sleep and chained to an X-shaped frame by plainclothes and uniformed agents as they sought information on activists involved in the protests and the role they believed Britain played in the demonstrations.

British Foreign Secretary Dominic Raab has summoned the Chinese ambassador in London to express the government’s outrage and demand Beijing investigate and hold those responsible accountable.

Chinese police in August announced Cheng’s release after 15 days of administrative detention but gave no details of the reasons behind his detention.

China’s ambassador to Britain, Liu Xiaoming, will “by no means accept the so-called concerns or complaints raised by the British side,” Chinese foreign ministry spokesman Geng Shuang said at a daily briefing on Wednesday.

“The Chinese ambassador to the U.K. will lodge the complaints with the U.K. to express our strong opposition and indignation to the U.K.’s wrong words and deeds on Hong Kong in these days,” Geng said.

Geng did not address Cheng’s allegations directly, but cited a statement by Shenzhen police from August saying his lawful rights had been been protected and that he had “admitted his offense completely,” an apparent reference to a confession of soliciting prostitution that Cheng says was coerced. Cheng has strongly denied the charge.

Police in Shenzhen did not immediately respond to faxed questions about Cheng’s allegations.

Cheng worked for the consulate as a trade and investment officer with a focus on attracting Chinese investment in Scotland. That required him to travel frequently to mainland China and he was detained at the border with Hong Kong after returning from a one-day business trip.

Opposition to proposed extradition legislation that could have allowed suspects in Hong Kong to be extradited to face possibly unfair trials in China provided the initial spark for the Hong Kong protests, which later morphed into a broader anti-government and pro-democracy movement.

China says it doesn’t allow suspects to be tortured or make false confessions, although both practices are believed to be common.