Donald Trump has threatened to spark a new row over intelligence-sharing between Britain and the US after he claimed the Parsons Green Tube bombers had been “in the sights” of Scotland Yard.

In a trademark tweet, the US president called for a “proactive” response to dealing with the terrorist threat.

“Another attack in London by a loser terrorist,” he wrote. “These are sick and demented people who were in the sights of Scotland Yard. Must be proactive!”

His comments, which did not correspond with information released by the Metropolitan Police, were condemned as “unhelpful” by former No 10 aide Nick Timothy.

“True or not - and I’m sure he doesn’t know - this is so unhelpful from leader of our ally and intelligence partner,” he tweeted.

Scotland Yard refused to be drawn on the remarks. A spokeswoman said: “It is not something we would comment on.”

Another attack in London by a loser terrorist.These are sick and demented people who were in the sights of Scotland Yard. Must be proactive! — Donald J. Trump (@realDonaldTrump) September 15, 2017 Loser terrorists must be dealt with in a much tougher manner.The internet is their main recruitment tool which we must cut off & use better! — Donald J. Trump (@realDonaldTrump) September 15, 2017 The travel ban into the United States should be far larger, tougher and more specific-but stupidly, that would not be politically correct! — Donald J. Trump (@realDonaldTrump) September 15, 2017

There was no immediate response from the White House to questions as to the basis of Mr Trump’s assertion.

However, it comes after British police temporarily suspended intelligence-sharing with the US in the wake of the Manchester Arena bombing in May following a series of leaks to American media.

CBS disclosed the name of the bomber, Salman Abedi, citing US sources, at a time when the British authorities were asking media to withhold the information to protect the investigation.

The New York Times then published detailed photographs taken from the bomb scene which had been taken by British investigators.

The “special relationship” had already come under strain earlier in the year, when the then White House press secretary Sean Spicer repeated claims that GCHQ, the UK surveillance agency, had been involved in bugging the Trump campaign on behalf of Barack Obama.

His comments drew a rare public statement from GCHQ denouncing the allegation as “utterly ridiculous”.

London Mayor Sadiq Khan, who clashed with Mr Trump over his response to the London Bridge terror attack, would not be drawn on the president’s latest comments.

“I’ve simply been too busy this morning to look at my Twitter,” he told LBC Radio. “My priority is making sure that we do what we can to keep Londoners safe.”

A City Hall source said: “He hopes people don’t speculate on things before we know the full facts. That’s quite clear what he thinks about that.”

PA