The hoax messages trick played on Andy Burnham was the work of a Russian cyber warfare unit, it was claimed yesterday.
The Prime Minister said last week that he was not embarrassed to have exchanged messages with a person posing as Donald Trump's chief of staff.
He played down any security leak, insisting that his communication with a person pretending to be White House aide Susie Wiles amounted to 'minimal exchange of information of zero consequence'.
But sources told The Mail on Sunday that the scam was the work of a unit called Centre 16 which operates within the Kremlin's secretive Federal Security Service (FSB) – and reports directly to Vladimir Putin.
They said the Government Communications Headquarters (GCHQ) and MI5 had identified a 'call pattern' through signal mapping and electronic surveillance that can generate the caller's number and location.
The sources declined to confirm that the call was made directly from Russia. But they added that the UK had developed capabilities to intercept phone data from so-called 'burner phones' by 'interrogating' the SIM card and 'geo-locating' where they are being used from.
One source said: 'All the indicators from this incident point to the Kremlin. What is unclear is how they got the phone number [of Mr Burnham]. That is still being investigated.'
On Saturday night, it was reported that ex-foreign secretary David Lammy had given the PM the number that he mistakenly thought was for Ms Wiles.
Andy Burnham insisted that his communication with a person pretending to be White House aide Susie Wiles amounted to 'minimal exchange of information of zero consequence'
Sources told The Mail on Sunday that the scam was the work of a unit called Centre 16 which operates within the Kremlin's secretive Federal Security Service (FSB) – and reports directed to Vladimir Putin
Analysts have assessed that the phone 'scamming' of UK politicians by Moscow is a provocation to show that Putin has the upper hand in electronic warfare on the political stage.
However, last week, the Liberal Democrats called for an investigation into the White House hoax.
Lib Dem MP James MacCleary wrote to Parliament's intelligence and security committee to ask it to consider an inquiry into what he called 'an egregious security breach'.
The Prime Minister said the 'correct action' had been taken in response to the hoax both in the UK and US, but did not provide any details.