The trio, aged 39, 43 and 68, were arrested on Wednesday by counter-terrorism officers in London and Wales on suspicion of assisting a foreign intelligence service.

All three had "subsequently been released on bail to a date in May", London's Metropolitan Police said in a statement.

Chinese espionage is a politically sensitive subject in Britain and the case could become awkward for Starmer who visited Beijing recently aiming to reset relations with the Asian giant.

Media reported that the husband of Labour lawmaker Joani Reid was among the three. Reid said Wednesday said she had never "seen anything to make me suspect my husband has broken any law".

Her husband David Taylor, 39, is listed as a "lobbyist" on her list of registered interests. According to his LinkedIn page, he works for Asia House, a think tank.

"I am not part of my husband's business activities and neither I nor my children are part of this investigation," she added.

The arrests came amid rising concerns over alleged Chinese espionage in the UK.

A spokeswoman for China's foreign ministry said: "We have always been against the hyping up of the so-called Chinese spy allegations, which tarnish China's image and mislead the public.

Starmer has been criticised by opposition politicians, human rights groups and US President Donald Trump for approving a massive new Chinese embassy in London and for his Beijing visit.

The UK leader has repeatedly defended the visit, the first by a British prime minister since 2018, as important step to closer ties with the world's second largest economy.