Liz Truss's personal phone was hacked by agents suspected of working for Russian President Vladimir Putin, The Mail on Sunday can reveal.
    They gained access to top-secret details of negotiations with key international allies – as well as private messages she exchanged with her close friend Kwasi Kwarteng.
    The hack was discovered during the summer Tory leadership campaign, when Ms Truss was Foreign Secretary, but the details were suppressed by the then Prime Minister Boris Johnson and the Cabinet Secretary Simon Case.
    One source said the phone was so heavily compromised that it has now been placed in a locked safe inside a secure government location.
    It is understood that the messages that fell into foreign hands included criticisms of Mr Johnson made by Ms Truss and Mr Kwarteng, leading to a potential risk of blackmail.
    They are also believed to have included highly sensitive discussions with senior international foreign ministers about the war in Ukraine, including detailed discussions about arms shipments.
    In a statement released to the MoS on Saturday afternoon, a UK Government spokesperson said: 'We do not comment on individuals' security arrangements.'
    But a source with knowledge of the incident said: 'This caused absolute pandemonium. It is not a great look for the intelligence services if the Foreign Secretary's phone can be so easily plundered for embarrassing personal messages by agents presumed to be working for Putin's Russia.'
    The security services have grown increasingly concerned about the threat posed by hackers working for hostile countries such as Russia and China, with mobile phones regarded as the 'soft underbelly' of the modern state.
    An Israeli system called Pegasus, which gains access to phones without the owner knowing, can be launched on phones with a text message. It then runs in the background without the owner's knowledge, gaining access to everything on the device and tracking the individual's movements.