British Prime Minister Rishi Sunak has expressed "very strong concerns" to Chinese Premier Li Qiang following arrests of British citizens alleged to have spied for China.
The two leaders met on Sunday on the sidelines of the G20 summit in New Delhi.
The Sunday Times reported on the same day that London's Metropolitan Police had arrested two British nationals in March on suspicion of spying for China.
The British newspaper said one of the suspects was a parliamentary researcher who gathered information for lawmakers engaged in foreign policy. He reportedly had been recruited in China and is suspected to have attempted to influence lawmakers who are critical of China.
Sunak told reporters that he had raised "very strong concerns about any interference in our parliamentary democracy, which is obviously unacceptable."
China's foreign ministry quoted Li as having told Sunak that "the two sides should properly handle their differences."
Britain and China are seeking to mend ties. Last month, foreign ministers from the two countries met for the first time in five years. But it remains uncertain how things will unfold due to a lingering sense of caution against China within Britain.