The British government has lashed out at China over its alleged torture of a former worker at the U.K.'s Hong Kong consulate.

Simon Cheng was detained for 15 days on a trip to mainland China in August while working for the British government in his native Hong Kong, accused of inciting unrest in the city.

In a lengthy blog post, Cheng has claimed he was blindfolded, shackled, hooded, beaten and forced to hold stress positions for hours at a time by Chinese secret police during his detention.

In a statement Wednesday, U.K. Foreign Secretary Dominic Raab said: "We were shocked and appalled by the mistreatment he suffered while in Chinese detention, which amounts to torture."

"I summoned the Chinese Ambassador to express our outrage at the brutal and disgraceful treatment of Simon in violation of China's international obligations. I have made clear we expect the Chinese authorities to investigate and hold those responsible to account."

Raab added that the Foreign and Commonwealth Office (FCO) is working to support Cheng and his fiancée, including the possibility of allowing them to come to the U.K.