The UK’s domestic spy service MI5 on Tuesday warned politicians that Chinese spies were actively reaching out to “recruit and cultivate” them on the professional networking site, LinkedIn.

Writing to lawmakers, House of Commons Speaker Lindsay Hoyle said a new MI5 espionage alert warned that Chinese nationals were using profiles on the platform to “conduct outreach at scale” on behalf of China’s security services.

“Their aim is to collect information and lay the groundwork for long-term relationships, using professional networking sites, recruitment agents and consultants acting on their behalf,” Hoyle said.

MI5 issued the alert because the activity was “targeted and widespread,” he added.

Security Minister Dan Jarvis said that apart from parliamentary staff, others including economists, think tank consultants and government officials have been similarly targeted.

“This activity involves a covert and calculated attempt by a foreign power to interfere with our sovereign affairs in favour of its own interests and this government will not tolerate it,” Jarvis told parliament on Tuesday.

British intelligence officials have steadily ramped up their warnings in recent years about espionage threats from China, the UK’s third biggest trading partner.

MI5 Director-General Ken McCallum told reporters last month that Chinese state actors present a national security threat to the UK “every day.”

The latest warning comes two months after the collapse of a case against two British men accused of spying on UK lawmakers for Beijing.

The UK’s top prosecutor said the charges were dropped because the government had refused to designate China as an “enemy” and a threat to national security. Prime Minister Keir Starmer has denied claims of government interference in the case.

In January 2022, MI5 issued a similar security alert to all lawmakers warning that a London-based lawyer was “involved in political interference activities” in the UK on behalf of China’s Communist Party.

The lawyer, Christine Lee, was accused of facilitating covert donations to British parties and legislators “on behalf of foreign nationals.”

Although not charged with any criminal offence, Lee later sued MI5, arguing that its alert was politically motivated and violated her human rights. She lost the case last year.