London (dpa) - British Foreign Secretary Dominic Raab on Wednesday said he had summoned the Chinese ambassador to protest the "brutal and disgraceful" treatment of a former Hong Kong consular employee who alleged that he was tortured by Chinese police.

Simon Cheng Man-Kit wrote that he was accused of spying and subjected to "torture, threats and coercion." This included being handcuffed to a "tiger chair" - a device used to immobilize suspects and deprive them of sleep - during a 15-day detention in southern China in August.

"I summoned the Chinese ambassador [on Tuesday] to express our outrage at the brutal and disgraceful treatment of Simon in violation of China's international obligations," Raab said in a statement.

He said Britain expects Beijing to "investigate and hold those responsible to account."

The Chinese embassy said ambassador Liu Xiaoming "expressed grave concern and strong opposition to British government’s recent repeated wrong remarks regarding Hong Kong."

Liu told Raab said that Cheng had "confessed all his offences, and all his lawful rights and interests were guaranteed in accordance with law," the embassy said in a statement.

In another sign of a growing rift between London and Beijing over Hong Kong, British activists criticized a travel ban on Hong Kong protest leader Joshua Wong.

Tom Tugendhat, a lawmaker from Prime Minister Boris Johnson's Conservatives, urged Britain to "question the nature of its relationship with China."

The unrest in Hong Kong is one of several "signs of a world to come if the UK and allies don’t wake up to a changing order," Tugendhat tweeted.

Wong tweeted that a Hong Kong court's travel ban had "imposed an extra punishment before I was convicted guilty."

Benedict Rogers, a Conservative and Catholic human rights activist, said the travel ban was "absolutely appalling and incredibly sad."

Wong had been due to receive the annual Westminster Award for human rights from Right to Life UK on December 12.

Cheng, 28, was a trade and investment officer at the British consulate in Hong Kong at the time he was detained.

He said he travelled to the southern Chinese city of Shenzhen, which borders Hong Kong, on August 8 for a business trip.

Police stopped him at a border railway station as he was about to return to Hong Kong.

Cheng said he was taken to several police stations and detention centres, where he faced threats, blindfolding and shackling during repeated interrogation by uniformed police and plain-clothes state security officers.

The police accused him of spying and helping to organize anti-government protests in Hong Kong.

Cheng said he was forced into a confession for "soliciting prostitution," a charge he denies.

Rogers, who co-founded the rights group Hong Kong Watch, said the international community must act "to insist that the crisis in Hong Kong can only be resolved if there is a de-escalation of violence, a meaningful dialogue [and] positive steps towards political reform."

Any reform must lead to universal suffrage and an independent inquiry into brutality by Hong Kong police, he wrote on the website Conservative Home on Wednesday.

"If these demands continue to be unheeded, Hong Kong is dead," Rogers said.

Britain handed control of Hong Kong to China in 1997 after more than 150 years of colonial rule.