Russian military hackers have targeted the messaging app at the centre of the White House group chat fiasco, raising further fears about the security of US secret communications.

Researchers at Google found cyber attackers linked to the Kremlin’s military intelligence agency had sought to gain access to Signal accounts in Ukraine and were likely to use the techniques on other targets to snoop on conversations.

On Monday it emerged that members of Donald Trump’s cabinet including JD Vance, the vice president, Marco Rubio, the secretary of state, and Pete Hegseth, the defence secretary, had used Signal to discuss secret US military plans.