The meeting comes just hours after it emerged a British parliamentary researcher accused of spying for China had been arrested, along with another man in Oxfordshire.
Downing Street confirmed the Prime Minister met his Chinese counterpart on the margins of the G20 summit in India for an informal discussion on Sunday.
A House of Commons researcher was arrested under the Official Secrets Act on suspicion of spying for China.
The man, who is in his 20s, was arrested in Edinburgh by officers from the Met’s Counter Terrorism Command.
The Sunday Times reported the British national holds a parliamentary pass, has links to several prominent Conservative MPs, including security minister Tom Tugendhat and foreign affairs committee chairwoman Alicia Kearns, and previously lived and worked in China.
Ms Kearns said she was “aware” of the report but would “not be commenting”.
Mr Tugendhat is said not to have had any contact with the researcher since before he became security minister in September last year.
Met officers also arrested another man, in his 30s, at a property in Oxfordshire while searches were carried out at a property in east London.
The arrests took place on March 13.
A report from Parliament’s spy agency watchdog, the Intelligence and Security Committee, warned in July that Beijing is targeting the UK “prolifically and aggressively”.
Mr Sunak has faced criticism from some senior Torys of seeking a relationship with a China they see as increasingly a threat.
Foreign Secretary James Cleverly visited Beijing amid the criticism, insisting the UK would have a “pragmatic” relationship with China to tackle major global issues such as climate change.
Justice Secretary Alex Chalk told Sky News’ Sunday Morning with Trevor Phillips: “The Prime Minister has been very clear when it comes to China it is an epoch-defining threat, challenge, forgive me, so of course we have got to take it extremely seriously.
“I know that the police and no doubt other agencies will take it as seriously as well, and let’s learn whatever lessons need to be learned.”
Asked whether the parliamentary pass system needed to be made more secure, he said: “There is a rigorous approach that is taken in terms of being provided with passes, but plainly this has got to play through in terms of this investigation, and whatever lessons need to be learned by the parliamentary authorities I am sure will be learned.”