British Prime Minister Theresa May lashed out at President Trump for suggesting in a tweet that Friday’s London subway terrorist had been known to police.

May said that his assertion was not “helpful” and that authorities were still investigating the “full circumstances” surrounding the attack, which injured at least 22 people.

In his tweetstorm, Trump referred to the attacker as a “loser terrorist.”

“These are sick and demented people who were in the sights of Scotland Yard. Must be proactive!” he said.

“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!” he added.

After chairing a meeting of the Cobra emergency committee, May said: “I never think it is helpful for anybody to speculate on what is an ongoing investigation,” the Telegraph reported.

“As I have just said the police and security services are working to discover the full circumstances of this cowardly attack and to identify all those responsible,” she said.

Trump told reporters Friday morning that he had been briefed on the explosion and said he planned to call May.

“It’s a terrible thing,” he said. “It keeps going and going, and we have to be very smart and we have to be very, very tough — perhaps we’re not nearly tough enough.”

Scotland Yard has yet to confirm whether the person behind the fiery explosion had been on authorities’ radar, the paper reported.

Trump has come under fire before after weighing in on terror attacks in the UK.

In June, he blasted London Mayor Sadiq Khan for telling residents after an attack at London Bridge that there was “no reason to be alarmed” by an increased police presence.

Misinterpreting what Khan said, Trump fired off a tweet saying: “At least 7 dead and 48 wounded in terror attack and Mayor of London says there is ‘no reason to be alarmed!’”

Khan, the British capital’s first Muslim leader, called the tweet “ill-informed.”

Scotland Yard also delivered a rebuke to Trump’s tweets Friday.

“The comments are unhelpful and pure speculation. If anyone has got any evidence or information, please contact the anti-terrorism hotline,” a Yard spokesman said, according to the Telegraph.

Nick Timothy, a former senior aide to May, echoed London police’s comments.

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

Trump has also been mocked before for calling terrorists “losers.”

In May, he called the terrorists who killed 22 people at an Ariana Grande concert in Manchester “evil losers.”

“I won’t call them ‘monsters’ because they’d like that term,” Trump said at the time.