Foreign Secretary James Cleverly repeatedly refused to answer questions about whether he raised the arrest of a parliamentary researcher accused of spying for China with officials in Beijing.
Both were held on suspicion of offences under Section 1 of the Official Secrets Act 1911, which punishes offences that are said to be “prejudicial to the safety or interests of the state”.
They were bailed until early October but the researcher said on Monday morning he was “completely innocent”.
Speaking to Sunday with Laura Kuenssberg on BBC One, Mr Cleverly said: “We do not comment on intelligence or security-related matters.
“The Prime Minister is absolutely right that both he and I raised with the Chinese authorities their actions which are seeking to undermine or distort our democracy.”
Pressed about the matter, Mr Cleverly continued to repeat his refusal to comment on such matters.
Earlier on Sunday, Mr Cleverly told Sky News’ Trevor Phillips: “There is incredibly important work to do. And the advocates of somehow ignoring China, pretending it doesn't exist, not talking to China, not having an embassy in Beijing, and not having a Chinese embassy in the UK.
“Some people have said that we should disengage from China. That is not a credible option.
“When there is a difficult relationship - and this is a challenging and difficult relationship - it is more important rather than less important that you maintain those face-to-face communications.”
After the arrests were revealed by The Sunday Times last weekend, Rishi Sunak said he raised concerns with Chinese Premier Li Qiang at the G20 summit.
Prompted by questions from Sir Keir Starmer during PMQs on Wednesday, Mr Sunak told MPs: “ I have been emphatically clear in our engagement with China that we will not accept any interference in our democracy and parliamentary system.
“This includes sanctioning of MPs and malign activity, such as the type of activity alleged to have taken place.
“I can absolutely confirm that the Foreign Secretary raised these issues on his recent visit and I also reinforced this in my meeting at the G20.”
The researcher at the centre of the row had links with senior Tories including security minister Tom Tugendhat and Foreign Affairs Committee chairwoman Alicia Kearns.
In a statement released through his lawyers, the 28-year-old researcher - who has not been officially named by police or MPs - said: “I feel forced to respond to the media accusations that I am a ‘Chinese spy’.
“It is wrong that I should be obliged to make any form of public comment on the misreporting that has taken place.
“However, given what has been reported, it is vital that it is known that I am completely innocent.
“I have spent my career to date trying to educate others about the challenge and threats presented by the Chinese Communist Party.
“To do what has been claimed against me in extravagant news reporting would be against everything I stand for.”
A Chinese embassy spokesperson added: “The claim that China is suspected of ‘stealing British intelligence’ is completely fabricated and nothing but malicious slander.
“We firmly oppose it and urge relevant parties in the UK to stop their anti-China political manipulation and stop putting on such self-staged political farce.”