LONDON (AP) — Prime Minister Rishi Sunak chastised China’s premier on Sunday for “unacceptable” interference in British democracy, after a newspaper reported that a researcher in Parliament was arrested earlier this year on suspicion of spying for Beijing.

Sunak said he raised the issue with Premier LI Qiang when the two met at a Group of 20 summit in India. He told British broadcasters in New Delhi that he’d expressed “my very strong concerns about any interference in our parliamentary democracy, which is obviously unacceptable.”

The two men met after the Metropolitan Police force confirmed that a man in his 20s and a man in his 30s were arrested in March under the Official Secrets Act. Neither has been charged and both were bailed until October pending further inquiries.

The Sunday Times reported that the younger man was a parliamentary researcher who worked with senior lawmakers from the governing Conservatives, including Alicia Kearns, who now heads the powerful Foreign Affairs Committee, and her predecessor in that role, Tom Tugendhat, who is now security minister. The newspaper said the suspect held a pass that allows full access to the Parliament buildings, issued to lawmakers, staff and journalists after security vetting.

Tensions between Britain and China have risen in recent years over accusations of economic subterfuge, human rights abuses and Beijing’s crackdown on civil liberties in the former British colony of Hong Kong.

Britain’s Conservatives are divided on how tough a line to take with Beijing and on how much access Chinese firms should have to the U.K. economy. More hawkish Tories want Beijing declared a threat, but Sunak has referred to China’s growing power as a “challenge.”

Former U.K. Conservative leader Iain Duncan Smith said news of the March arrests “gives the lie to the government’s attempt not to see China as a systemic threat.”

U.K. spy services have sounded ever-louder warnings about Beijing’s covert activities. In November, the head of the MI5 domestic intelligence agency, Ken McCallum, said “the activities of the Chinese Communist Party pose the most game-changing strategic challenge to the U.K.” Foreign intelligence chief Richard Moore of MI6 said in July that China was his agency’s “single most important strategic focus.”

In January 2022, MI5 issued a rare public alert, saying a London-based lawyer was trying to “covertly interfere in U.K. politics” on behalf of the Chinese Communist Party. It alleged attorney Christine Lee was acting in coordination with the Chinese ruling party’s United Front Work Department, an organization known to exert Chinese influence abroad.

An opposition Labour Party lawmaker, Barry Gardiner, received more than 500,000 pounds ($685,000) from Lee between 2015 and 2020, mostly for office costs, and her son worked in Gardiner’s office. Lee and the Chinese government both deny wrongdoing.

China has repeatedly criticized what it calls British interference in its internal affairs and denied meddling in the politics of foreign nations.

Sunak and Li met days after Foreign Secretary James Cleverly visited Beijing, the highest-level trip by a British politician to China for several years. Chinese President Xi Jinping did not attend the G20 meeting in India

Sunak defended his approach of cautious engagement, saying “there’s no point carping from the sidelines – I’d rather be in there directly expressing my concerns, and that’s what I did today.”