The Conservative Party dropped two potential candidates to become MPs after MI5 warned they could be Chinese spies, it has been reported.
It comes as ministers continue to face questions about allegations of espionage in Westminster after the arrest of a parliamentary researcher on suspicion of spying for Beijing.
The Times said the security service advised the Tory Party in 2021 and 2022 that the two MP hopefuls should not be included on the central list of candidates.
M15 is said to have raised concerns that the two people had links to the United Front Work Department - one of the key departments of the Chinese Communist Party - and were blocked from the list.
The newspaper cited an unnamed source as saying: “It was made very clear that they posed a risk.
“They were subsequently blocked from the candidates list. They weren’t told why.”
A Conservative Party spokesman said: “When we receive credible information regarding security concerns over potential candidates we act upon them.”
Tory candidates are vetted by the party and subject to criminal record checks and an interview. A Tory party source told The Times that in the past M15 had given a “nudge” if it had concerns about candidates.
The claims will fuel debates about the UK’s relationship with China following the arrest of a staffer under the Official Secrets Act.
The Briton was arrested along with another man by officers on March 13 on suspicion of spying for Beijing, it was revealed by the Sunday Times.
Officers from the Metropolitan Police’s Counter Terrorism Command, which oversees espionage-related offences, are investigating.
One of the men, in his 30s, was detained in Oxfordshire on March 13, while the other, in his 20s, was arrested in Edinburgh, Scotland Yard said.
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 have been bailed until early October.
The arrests were only revealed at the weekend and 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.
The allegations have led to increased pressure from China “hawks” on the Tory benches for Prime Minister Rishi Sunak to toughen his stance towards Beijing.
James Cleverly became the first Foreign Secretary in five years to visit China, amid efforts to develop more pragmatic ties with the country.
Mr Sunak on Monday insisted that Mr Cleverly raised the issue of Chinese interference in UK democratic institutions during his recent trip and that he had “reinforced this” at the G20 summit.
But MPs have questioned whether it took reports of the arrest in March to be made public for the Prime Minister to raise concerns.
Deputy Prime Minister Oliver Dowden signalled that ministers could consider a tougher stance on China in the wake of the row.
