LONDON (REUTERS) - The British government said on Tuesday (March 1) it had not been granted access to a Hong Kong bookseller and British passport holder who disappeared last year.

In a television interview with China's Phoenix Television late on Monday (Feb 29), Lee Bo, a dual British and Hong Kong citizen, said he had returned to China voluntarily and would renounce his British citizenship.

Lee and four associates went missing over the past half year, sparking fears that Chinese authorities had abducted some of the men and taken them back to China. "Despite formal requests, we have not been granted consular access to Mr Lee," a British government spokesman said in a statement.

Lee's disappearances have provoked concern that China was using shadowy tactics to erode the "one country, two systems" formula under which Hong Kong has been governed since its return to China from British rule in 1997. At least one of the men faces charges for selling and distributing books critical of China's Communist Party leaders that are banned in China.

During the 20-minute interview with Phoenix Television, late on Monday (Feb 29), Lee gave the first detailed account of his disappearance from Hong Kong in December, saying he had returned to China voluntarily.

"I have always felt that I'm a Hong Kong citizen, a Chinese citizen, and because people have used my British nationality to sensationalise and make the situation more complicated, that's why I'm deciding to give up my British nationality," said Lee, who appeared calm in the interview.

"Why have I acted so mysteriously? It's because I've had to assist with a mainland Chinese investigation and it required testifying against some people."

Since he was afraid of reprisals from those he was testifying against, he said, "I used an illegal means to sneak there and I didn't use my (Chinese) home return permit."

Lee did not give details on how he'd crossed the border into China, or who helped him or when he might return. "This case is quite complicated ... so I need to be questioned for longer. I am very safe and free in China. My relations with law enforcement officers are very good. They treat me very well," he said.

Some politicians were sceptical and said Lee may have been pressured to try to erase perceptions of Chinese authorities carrying out illegal cross-border enforcement operations. "I don't know who helped him sneak over... Was he forced by Chinese police or state security agents?" said James To, a lawmaker with the Democratic Party. "There is still a big question mark."

Hong Kong Security Secretary Lai Tung-kwok said Hong Kong police would follow up to further clarify the circumstances of Lee's case, including how he had entered China.

Chinese Foreign Ministry spokesman Hong Lei, asked about Lee's appearance on television, noted that Lee and his wife had already made remarks on the case many times already.

"We should respect what they have said and respect the facts," he told a daily news briefing without elaborating. Lee's wife has previously said he travelled to the mainland voluntarily.

Four of the other Hong Kong booksellers, including Gui Minhai, a Swedish national, confirmed on Chinese television on Sunday (Feb 28) that they had been detained for "illegal book trading" in mainland China.