British police have stopped sharing evidence from the investigation into the terror network behind the Manchester bombing with the United States after a series of leaks left investigators and the government furious.
The ban is limited to the Manchester investigation only. British police believe the leaks are unprecedented in their scope, frequency and potential damage.
Downing Street was not behind the decision by Greater Manchester police to stop sharing information with US intelligence, a No 10 source said, stressing that it was important police were allowed to take independent decisions.
“This is an operational matter for police,” a No 10 spokesman said. The police and the Home Office refused to comment. The Guardian understands there is not a blanket ban on intelligence-sharing between the US and the UK.
Relations between the US and UK security services, normally extremely close, have been put under strain by the scale of the leaks from US officials to the American media.
After chairing a meeting of the emergency Cobra meeting Theresa May said: “I will make clear to President Trump that intelligence shared between our security agencies must remain secure.” She is due to meet the US president at a Nato summit in Brussels on Thursday.
Ahead of the summit, the prime minister said she would work with other leaders on the global effort to defeat terrorism and remove extremist material from the internet.
She said the domestic threat of terrorism is still at a critical level, meaning an attack may be imminent, and she urged the public to remain vigilant.
On Friday, the prime minister will attend a G7 summit in Taormina in Sicily, although her planned attendance is being cut short by a day because of the higher domestic terror threat level.
The prime minister said she will “lead a discussion on counter-terrorism and on how we will work together to prevent the plotting of terrorist attacks online and to stop the spread of hateful extremist ideology on social media”.
British officials were infuriated on Wednesday when the New York Times published forensic photographs of sophisticated bomb parts that UK authorities fear could complicate the expanding investigation, in which six further arrests have been made in the UK and two more in Libya.
It was the latest of a series of leaks to US journalists that appeared to come from inside the US intelligence community, passing on data that had been shared between the two countries as part of longstanding security cooperation.
A senior Whitehall source said: “These images from inside the American system are clearly distressing to victims, their families and other members of the public. Protests have been lodged at every relevant level between the British authorities and our US counterparts.
They are in no doubt about our huge strength of feeling on this issue. It is unacceptable.”
Whitehall sources reported a sense of deflation among UK security staff at the amount of detail coming out of America. The UK had shared the material with US police and intelligence in the expectation it would remain secret. The amount released is hampering at least part of the investigation, they believe.
Police chiefs also criticised the leaks. A national counter-terrorism policing spokesperson said: “We greatly value the important relationships we have with our trusted intelligence, law enforcement and security partners around the world.
“When that trust is breached it undermines these relationships, and undermines our investigations and the confidence of victims, witnesses and their families. This damage is even greater when it involves unauthorised disclosure of potential evidence in the middle of a major counter-terrorism investigation.”
Manchester’s mayor, Andy Burnham, added yet more criticism, saying the leaks were arrogant and disrespectful.
The ban on sharing information with the US on such a major inquiry is unprecedented, more so because the atrocity has potential implications for US efforts to prevent any similar attacks directed at American targets.
The ban is described as temporary, and British police are examining if they can put safeguards in place to stop any further leaks.
British police are angry that as their officers are in pursuit of a suspected terror network, with raids deemed so risky they are being carried out by elite armed officers, sensitive information is being regularly leaked by the US.
May will raise her concerns with the US president at the Nato summit, where she will push for the military alliance to join the coalition against Islamic State.
The images published by the New York Times revealed that the device used by Salman Abedi, which killed 22 people, had been made with “forethought and care”, raising questions for investigators about how it had been constructed and by whom.
Abedi had carried a metal box containing “well packed” explosives, metal nuts and screws in a box probably inside a Karrimor rucksack, the leaked details showed. The device was powerful enough for shrapnel to penetrate metal doors and to scar brick walls. Abedi detonated the bomb with his left hand.
It showed the force of the explosion was such that his torso was ripped from the rest of his body and propelled across the foyer and that most of those killed were in a circle around the bomber.
The kind of information that has been leaked is routinely shared with police counterparts in the US. The information goes into a shared computer system and is then distributed among different specialists in the US, ranging from bomb experts to those dealing in counter-terrorism.
The UK and US are among the closest intelligence partners in the world, with the UK’s surveillance agency, GCHQ, sharing information with the NSA, MI6 with the CIA, and MI5 with the FBI. But the lines are not rigid and information is often shared more widely.
On Wednesday Amber Rudd, the British home secretary, had rebuked the US security services for leaking the bomber’s name to American media before it had been made public in Britain, but her warnings appear to have had no impact.
“I have been very clear with our friends that that should not happen again,” Rudd said.