Jailed Hong Kong media tycoon Jimmy Lai's international legal team have asked UK Prime Minister Rishi Sunak for an urgent meeting ahead of his trial on national security charges later this year.

The trial on charges of colluding with foreign forces and sedition could see Mr Lai - who holds British nationality - spend the rest of his life in prison.

In the letter, seen by the BBC, Mr Lai's international legal team say they want to discuss "potential ways to secure Mr Lai's release".

The lawyers describe the case against him as "deeply concerning" and "emblematic".

Jimmy Lai has already been in detention for two years, facing numerous charges. In December he was sentenced to an additional five years and nine months for breaking a lease agreement at the newspaper's headquarters.

His supporters say all the charges against him are politically motivated.

Mr Lai founded pro-democracy newspaper Apple Daily. For more than 25 years his tabloid was seen as the only opposition newspaper in Hong Kong.

However, the newspaper was forced to close in June 2021 when its accounts were frozen and a number of senior staff were arrested under Hong Kong's national security law.

Beijing imposed the wide-ranging national security law on the former British colony in 2020.

The authorities say it was needed to restore order after a year of often violent protests. Critics say it is being used to silence political opponents of Beijing via the practice of "lawfare" - the use of the legal system as a political weapon.

Today the majority of the political opposition are either in prison or have fled the territory.

Mr Lai has long been considered the top target of the new legislation and his UK-based legal team has requested meetings with two consecutive foreign ministers, the first of which they say was rejected while the second went unanswered.

Earlier this month the UK government agreed for the team to meet a minister from the foreign office, the letter says.

In the letter, Caoilfhionn Gallagher KC also highlighted that the US government had condemned Mr Lai's conviction in October on fraud charges but the UK government had made no formal statement.

The British government confirmed that a junior foreign office minister had met Mr Lai's UK-based legal team on Tuesday.

The prime minister's spokesperson said: "We've been clear the Hong Kong authorities must end their targeting of pro-democracy voices, including Jimmy Lai."

Earlier, Mr Lai's son Sebastien told the BBC his father should not be behind bars.

"This is a man who for 20-odd years has given up a lot for democracy in Hong Kong which was something that was actually promised when the British handed Hong Kong back to China," he said.

Like his father, Sebastien is a British citizen. He lives in self-imposed exile in Taiwan. Since the arrest of his father under the national security law, he is unsure if he can return home.

"He is a British citizen who is in jail for championing these values we all take for granted that are sacrosanct to all of us," the 28-year-old said of his father.

Hong Kong was handed back to China from British control in 1997, but under a unique agreement - a mini-constitution called the Basic Law and a so-called "one country, two systems" principle.

They are supposed to protect certain freedoms for Hong Kong: freedom of assembly and speech, an independent judiciary and some democratic rights - freedoms that no other part of mainland China has.

However, the national security law makes it easier to prosecute protesters and critics say it has reduced the city's autonomy.

Mr Lai's trial has been adjourned to September 2023 with a ruling over who is allowed to represent him pending.

He had wanted British human rights lawyer Timothy Owen KC to represent him - but the Hong Kong government opposed this and the central Chinese government in Beijing has since ruled that Hong Kong's Chief Executive John Lee has the power to bar foreign lawyers from national security trials. However no final decision has yet been made.

"Lai's case is a test case for fair trials and free speech," said Eric Lai, a Hong Kong legal scholar.

The authorities have described the seriousness of his alleged crimes - colluding with foreign forces and sedition - as comparable to murder.

"Jimmy Lai is a traitor who is manipulated by foreign forces and sells his country for prosperity," Johnny Patriotic, a self-styled pro-Beijing activist who is frequently outside court during Mr Lai's appearances, told the BBC.

Sebastien Lai however said his father had not committed any crime.

"The crime is that he is in jail for this. The crime is ignoring it and not speaking out," he said.

• ·Two people have died and three others - including two children - are rushed to hospital following three-car horror smash in Pembrokeshire 
• ·Thailand dissolves parliament ahead of May election
• ·Lab leak divisions toxify Covid origins search
• ·Michelle Yeoh wants a seat at Hollywood
• ·Did Bollywood’s longest kiss really happen in 1933?
• ·Shah Rukh Khan's Pathaan a hit with fans and critics
• ·How China sneaks out America's technology secrets
• ·India watchdog probing Adani fraud allegations
• ·Two men arrested in connection with rape of LSU consequentlyrority student Madi Brooks have been released from jail: Casen Carver, 18, and Everett Lee, 28, post $125K bond
• ·How US Marines are being reshaped for China threat
• ·Imran Khan's chaotic court summons in 60 seconds
• ·How Gautam Adani's empire lost $100bn in days
• ·German train knife rampage victims are revealed to be girl, 17, and 19-year-old man: Suspect had been released from jail six days earlier 
• ·Covid losses mount in rural China: 'There are just too many'
• ·Australia buying more missiles to counter China
• ·Japanese Moon lander likely to have crashed