Ex-UK PM Truss' personal mobile phone was compromised by "agents suspected of working for Kremlin" when she was foreign minister, The Daily Mail reports, prompting UK opposition's demand for investigation.

Messages that reportedly fell into foreign hands included criticisms of Johnson made by Truss and Kwasi Kwarteng, who later became finance minister,
Messages that reportedly fell into foreign hands included criticisms of Johnson made by Truss and Kwasi Kwarteng, who later became finance minister, "leading to a potential risk of blackmail". (Reuters Archive)

UK opposition politicians have called for an investigation after a newspaper reported that suspected Kremlin agents had hacked ex-prime minister Liz Truss's cell phone when she was foreign minister.

In an unconfirmed report, The Daily Mail on Sunday cited unnamed security sources as saying that Truss's personal mobile phone had been hacked "by agents suspected of working for the Kremlin".

They are believed to have gained access to "top-secret exchanges with international partners".

A government spokesperson said: "We do not comment on individuals' security arrangements" but added that there are "robust systems in place to protect against cyber threats".

The report said the messages that fell into foreign hands included criticisms of Johnson made by Truss and Kwasi Kwarteng, who later became finance minister, "leading to a potential risk of blackmail".

Up to a year's worth of messages were downloaded, the report said, citing unnamed sources.

'Highly sensitive discussions'

Labour's Yvette Cooper, who focuses on homeland security, said the report raises "immensely important national security issues" including why and how the information was leaked.

"It is essential that all of these security issues are being investigated and addressed at the very highest level," she said.

Liberal Democrat foreign affairs spokesperson Layla Moran said: "We need an urgent independent investigation to uncover the truth."

A source told the paper the "compromised" phone has been placed inside a locked safe in a secure government location after up to a year's messages were hacked including "highly sensitive discussions" on the conflict in Ukraine.

The hacking was discovered in the summer when Truss was foreign minister and campaigning to become party leader and the next prime minister, the paper reported.

It claimed that "details were suppressed" by Johnson when prime minister and Simon Case, his most senior policy adviser.

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'Russia does this all the time'

The reported incident comes after Interior Minister Suella Braverman was reappointed by Prime Minister Rishi Sunak following her resignation over a security breach, in which she reportedly sent a top-secret document to an MP via her personal email.

The article did not make clear on what basis Russia was suspected to be behind the alleged attack.

But it quoted a security source as saying: "It takes a while to track who is behind attacks like these, but Russia tends to top the list."

Former Tory leader, MP Iain Duncan Smith told the newspaper: "Russia does this all the time."

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Source: TRTWorld and agencies