The daughter of jailed Hong Kong democracy tycoon Jimmy Lai has expressed concern about her father’s deteriorating health in prison, saying his fingernails “sometimes fall off” and his teeth are rotting.

Lai, 78, has been detained since December 2020 and faces life in prison. earlier this month he was convicted Collusion with foreign powers under Hong Kong’s controversial national security law (NSL).

Chinese authorities deny Lai was mistreated in prison and say he is in “good health”.

The BBC has seen a letter written by Lai’s family urging Prime Minister Keir Starmer to call for Lai’s release when he meets with Chinese President Xi Jinping next month.

His daughter Claire Lai, who lives in exile in London, told the BBC she feared she “may never see him again”.

“I certainly fear that my father will become a martyr, and I don’t want him to become a martyr. But I wouldn’t be here today, and I wouldn’t be speaking out if I didn’t think this was his best chance to be reunited with our family.”

She described her father as an “extremely strong man” when he was jailed, but he had “lost a lot of weight” over the past year.

“He was diabetic and had heart problems he had never had before. His fingernails turned purple-grey and sometimes fell off. His teeth were rotting.

“He had back and waist pain. Sometimes it was painful for him to stand up. Sometimes he couldn’t stand up. Sometimes he couldn’t even get out of bed.”

Jimmy Lai’s family has repeatedly expressed concerns about his deteriorating health. Sebastian told the BBC earlier this year His father’s “body was falling apart.”

Spokesperson of the Office of the Commissioner of the Ministry of Foreign Affairs in Hong Kong said earlier this month Jimmy Lai’s “legitimate rights and interests are fully protected and he is in good health.”

They added that “Lebanon was provided with a safe, humane, appropriate and healthy detention environment in accordance with the law.”

British citizen Jimmy Lai is the most high-profile person to be charged under the national security law. The law was introduced in 2020 in response to massive pro-democracy protests in Hong Kong.

Beijing defends the law as necessary to maintain Hong Kong’s stability, but critics say it effectively bans dissent.

Jimmy Lai is accused of lobbying foreign governments to impose sanctions on Hong Kong and China. He was also found guilty under a separate colonial-era law for publishing inflammatory material in the now-defunct Apple Daily newspaper.

After Jimmy Lai was convicted earlier this month, the UK denounced it as “politically motivated persecution”, saying he was “targeted for peacefully exercising his right to free speech…”.

The Foreign, Commonwealth and Development Office said: “The UK has repeatedly called for the National Security Act to be scrapped and for an end to the prosecution of all individuals charged under it.”

Chinese authorities said in a statement earlier this month that Western attempts to “influence judicial decisions through political pressure are a blatant violation of the spirit of the rule of law and fully expose their hypocritical ‘double standards.’ China firmly opposes this.”

Starmer will visit China in late January 2026. This will be the first visit to China by a British Prime Minister since 2018.