MI5 has warned politicians they are being targeted by foreign spies as concern intensifies over plots to influence and sway public debate.

MI5’s National Protective Security Authority told MPs, peers, councillors, candidates and parliamentary staff to “remain alert and trust their instincts”.

The intelligence agency said spies could pose as “diplomats, journalists, academics or lobbyists”, or use people working in those fields as “proxies” for espionage work.

MI5 Director General, Sir Ken McCallum, said: “When foreign states steal vital UK information or manipulate our democratic processes they don’t just damage our security in the short-term, they erode the foundations of our sovereignty and ability to protect our citizens’ interests.

“Everyone reading this guidance cares deeply about the role they play in UK democracy. Take action today to protect it – and yourself.”

Security minister Dan Jarvis told the Commons the advice would help politicians “better understand the threat” posed by countries including Russia, China and Iran.

As well as urging vigilance at home, MI5’s advice warned that foreign intelligence services could seek to exploit politicians’ overseas travel to access their data or use financial donations as a route to influence.

It said: “What might begin as an apparently genuine interaction can transition into something more malign. It’s important you remain alert and trust your instincts.”

The advice follows the collapse of the trial of two alleged Chinese spies, one of whom worked as a parliamentary researcher and was closely linked to senior Conservatives at the time of the alleged offences.

But MI5 and the Home Office pointed to other attempts by foreign governments to interfere in British politics, including Reform UK’s former Welsh leader, Nathan Gill, who pleaded guilty to receiving bribes to make pro-Russian statements while an MEP.

Other cases included that of Christine Lee, a lawyer whom MI5 issued a warning to MPs about in January 2022, accusing her of being engaged in “political interference activities” on behalf of the Chinese Communist Party.

On Monday, Mr Jarvis told MPs the Government was “gravely concerned” about the security of Britain’s democratic institutions and was “crystal clear that our Parliament must and will be protected from espionage”.

While Monday’s guidance specifically accused Russia, China and Iran of carrying out “long-term strategic foreign interference and espionage”, the security service also warned that “other states” could seek to obtain information about “the UK system”.

And it suggested that foreign intelligence operatives could pose as “diplomats, journalists, academics or lobbyists”, or use people working in those fields as “proxies” for espionage work.

Conservative leader Kemi Badenoch, during an explosive Parliamentary debate, warned that by failing to prosecute two alleged spies, the Government had told Britain’s enemies they can get away with espionage.

And Mrs Badenoch accused Labour of trying to “curry favour” with Beijing.

Former Security Minister Tom Tugendhat also claimed the Government had created “more straw men than a Russian disinformation campaign.”

The director of public prosecutions Stephen Parkinson said the case collapsed after the Government failed to provide evidence that China was a threat.

ory leader Kemi Badenoch blasted Labour, telling MPs: “This is about the ineptitude

“China spied on us and they are issuing us with leaflets.

“The CPS had what it felt was a clear and compelling case to prosecute.

“But the trial has collapsed because for months and months, the Government has been refusing to give the CPS vital information.

“This wasn’t a mistake. This wasn’t a misunderstanding.

“This looks like a deliberate decision to collapse the case to curry favour with the regime in China. And instead of admitted this, the Security Minister has come here blaming the Official Secrets Act.

“If the Government does not prosecute those who spy on us, it sends a message to the public that the Government does not care about their safety.

“It sends a message to our allies who share intelligence with us that Britain cannot be trusted.

“And it sends a message to those who spy on us that they can get away with it.”

Mrs Badenoch, in a blistering attack, added in an emergency debate in Parliament: “Is it seriously the Government’s argument that no minister knew anything about this until the trial collapsed?

“If this is the case, it is astonishing.

“But my suspicion is that it is not the case. My suspicion is that ministers did know.

“They have the Chinese super embassy in their in-tray.

“They have the billion pounds compensation conversation they are allegedly being asked to pay for nationalising British Steel.

“I suspect that they have decided that closer economic ties with China were more important than due process and our national security.

“And if this is the case, if that was the decision of this Government, then they should just tell us that and have the backbone to admit it.

“They should explain it to the public. They should explain it to the CPS, they should explain it to our international allies and let them all be the judge.

“There is nowhere to hide.”

Security minister Dan Jarvis insisted that the Government did not withdraw or conceal any evidence in the China spy case.

He added: “For days, the party opposite has been making baseless claims that this Government deliberately collapsed an independent legal process through political interference.

“There is not a shred of evidence to back up any of those accusations that she’s made.”

Mr Jarvis added that Ms Badenoch had said in September last year that she had previously “shied away from calling China a threat”.

He said: “Every effort was made to provide evidence to support this case. The decision about whether to proceed with the prosecution was ultimately taken by the CPS, who were hamstrung by antiquated legislation that had not been updated by the previous Conservative government, despite the evolving nature of the state threats we face.

“The DPP (director of public prosecutions) has given his assurance that the CPS was not influenced by any external party, any member of this Government, nor any senior civil servant or special advisor working within it.

“Suggestions that the Government concealed evidence, withdrew witnesses or restricted the ability of witnesses to draw on particular bits of evidence, are all untrue.”