Beijing blasted Britain today for suggesting that a Hong Kong bookseller believed detained by China was "involuntarily removed to the mainland", accusing the former colonial power of interfering in Chinese domestic affairs.
Britain had earlier released a report describing the disappearance of Lee Bo, who holds a British passport and published books critical of Chinese politics, as a "serious breach" of an agreement signed with Beijing before Hong Kong was handed back to China in 1997.
They were Britain's strongest comments yet on a case that has rocked Hong Kong, adding to growing fears that freedoms are being eroded in the semi-autonomous city.
Beijing hit back, slamming London for making "groundless accusations against China".
"Hong Kong affairs are China's domestic affairs," foreign ministry spokesman Hong Lei said in a statement late today.
"We ask the British side to mind its words and actions and stop interfering in Hong Kong affairs."
Four other booksellers from the Hong Kong-based Mighty Current publishing house also disappeared in October and Chinese authorities have confirmed they are now under criminal investigation.
But questions remain over what has happened to Lee, 65, who went missing in December -- the only publisher to have disappeared from Hong Kong.
Letters purportedly written by Lee and sent to his wife confirmed he was now on the mainland and said he had gone to China of his own volition to help with unspecified investigations.
But Hong Kong lawmakers and activists have accused Chinese authorities of snatching Lee from the city, contravening laws that do not allow mainland police to operate within the territory.
"The full facts of the case remain unclear, but our current information indicates that Mr Lee was involuntarily removed to the mainland without any due process under Hong Kong SAR (Special Administrative Region) law," said Britain's foreign secretary Philip Hammond in a regular parliamentary report on Hong Kong.
"This constitutes a serious breach of the Sino-British Joint Declaration on Hong Kong and undermines the principle of 'One Country, Two Systems' which assures Hong Kong residents of the protection of the Hong Kong legal system."
Hammond said Britain had called for Lee's immediate return to Hong Kong and had been in communication with the Chinese government "at the highest level".
