The government is facing pressure to take stronger action against Beijing, after a parliamentary researcher was arrested amid accusations he spied for China.

Senior Conservative MPs have called for China to be categorised as a threat, a move backed by some cabinet ministers.

Rishi Sunak raised concerns about interference from Beijing with China’s premier while at the G20 in India.

The prime minister said an open dialogue with China was necessary.

Police confirmed on Saturday that two men, one in his 20s and another in his 30s, were arrested under the Official Secrets Act in March.

Sources have told the BBC one of them was a parliamentary researcher involved in international affairs issues.

As first reported in the Sunday Times, it is understood the researcher had links to several Conservative MPs.

The BBC has approached him for a response but is not naming him.

Both men have been released on bail, and the Met’s Counter Terrorism Command, which oversees espionage-related offences, is investigating.

The Sunday Times reported the researcher had links to security minister Tom Tugendhat and foreign affairs committee chairwoman Alicia Kearns, among others.

The arrest of the parliamentary researcher has renewed a debate which has been raging in the Conservative Party for months: Should the government take a stricter approach on China?

Ministers have so far resisted branding Beijing a threat.

The UK’s Foreign Secretary James Cleverly visited Beijing in August – the first such visit in five years – and told the BBC it would not be “credible” to disengage. But there are growing calls for a rethink.

Senior Tory backbenchers, including former leader Iain Duncan Smith and MP Tim Loughton, have called for the government to act.

Mr Duncan Smith said it was “time for us to recognise the deepening threat that the CCP (Chinese Communist Party) under (President) Xi now pose”.

And Mr Loughton warned about “how far the tentacles of the Chinese Communist Party (CCP) reach into British institutions”.

“Yet again the security of Parliament has potentially been compromised, reinforcing how we cannot view the CCP as anything other than a hostile foreign threat.”

Some cabinet ministers, such as Home Secretary Suella Braverman, are understood to support a tightening of the rules too.

Mr Sunak said on Sunday that he had raised “very strong concerns” about any interference in British democracy with China’s Premier Li Qiang.

But he also said the UK should not be “carping from the side-lines” and it was better to be in the room raising concerns.

Justice Secretary Alex Chalk defended the current stance towards China on BBC One’s Sunday with Laura Kuenssberg programme,

He said the UK was right to “engage” with the country but Mr Sunak had highlighted the need to “proceed with caution”.

Parliament’s Intelligence and Security Committee issued a long-awaited report in July, warning the government had been slow to come to terms with the security risks from Beijing.

“It appears that China has a high level of intent to interfere with the UK government, targeting officials and bodies at a range of levels to influence UK political thinking and decision-making relevant to China,” the report said.