Hong Kong businessman and British national Jimmy Lai must be released unconditionally and immediately from prison, a group of MPs and their allies across the world have said as his trial recommences.

Conservative former leader Sir Iain Duncan Smith, former chancellor Jeremy Hunt, and Labour former minister Dame Meg Hillier are among the senior political figures to have joined calls for Mr Lai’s release.

Pro-democracy supporter Mr Lai was jailed in late 2020 in Hong Kong, and is currently being held in solitary confinement after being accused of violating the territory’s new national security law.

Mr Lai, who founded the now defunct Apple Daily newspaper, has pleaded not guilty to charges of collusion with foreign forces and sedition, and faces life behind bars if convicted.

Sir Keir Starmer raised his case with Chinese President Xi Jinping at the G20 summit in Brazil on Monday, in a sign he was prepared to challenge Beijing over human rights abuses.

As the 76-year-old’s trial is set to recommence in Hong Kong, 105 politicians from 24 countries – including 23 MPs and seven peers – have joined forces to call for the court proceedings to cease and for Mr Lai’s immediate release.

A joint statement co-ordinated by Alicia Kearns, a shadow Foreign Office minister, warns Mr Lai’s health is “deteriorating” and describes his trial as being “tainted with unfairness”.

It adds: “It is before hand-picked judges, evidence allegedly obtained by torture is being used against him, and it has been subject to lengthy delays.

“Meanwhile Jimmy Lai, a practising Catholic, has been denied Holy Communion for almost a year.

“On the eve of the recommencement of his trial, we urgently demand Jimmy Lai’s immediate and unconditional release.”

Ms Kearns, the MP for Rutland and Stamford, told the PA news agency: “Jimmy Lai is being inhumanely persecuted for standing up for basic human values. He represents the flame of freedom millions seek around the world.

“We have a duty to fight for Jimmy Lai as a British citizen, and to take a stand against the Chinese Community Party’s erosion of rule of law in Hong Kong.

“This letter represents the strength of international feeling and commitment of parliamentarians globally to securing Jimmy Lai’s immediate release and return to the UK with his family.”

Sebastien Lai, the businessman’s son, said: “The Prime Minister has made clear in Parliament that my father’s case is a priority for the Government and that he should be immediately released.

“I expect this to be a key issue for discussion between the Prime Minister and President Xi at the G20, and hope that they can agree a speedy solution which saves my father’s life. This would protect both the UK’s and China’s interests.”

At the G20 summit, Sir Keir told President Xi he “wanted to engage honestly and frankly” on issues where the UK disagrees with China.

The Prime Minister raised Mr Lai’s case with the Chinese premier during a bilateral meeting on Monday, but journalists were ushered out of the room as he told Mr Xi the UK was “concerned by reports of Jimmy Lai’s deterioration”.