The Ministry of Defence is offering soldiers to support armed police in London after dozens of Met officers stood down from firearms duties.
According to reports, more than 100 officers have turned in permits allowing them to carry weapons, there are more than 2,500 armed officers in the Met.
Police said the action was being taken after an officer was charged with the murder of unarmed Chris Kaba, 24.
Met chief Sir Mark Rowley welcomed a Home Office review into armed policing.
In an open letter to the home secretary, he said it was right his force was “held to the highest standards” – but the current system was undermining his officers and suggested they needed more legal protections.
A Met Police officer appeared in court on Thursday.
In a statement, the Met said some officers were “worried” about how the Crown Prosecution Service decision to bring a charge “impacts on them”.
The MoD said it received a request – known as Military Aid to the Civil Authorities MACA – from the Home Office to “provide routine counter-terrorism contingency support to the Metropolitan Police, should it be needed”.
A MACA is offered to the police or the NHS in emergency situations – the military helped medical staff in the Covid pandemic and covered for striking border staff and paramedics last year.
The Met said it was a “contingency option” that would only be used “in specific circumstances and where an appropriate policing response was not available”.
Military staff would not be used “in a routine policing capacity”, it added.
Last saturday, the Met said its own officers still make up the vast majority of armed police in the capital but they were being supported by a limited number of firearms officers from neighbouring forces.
According to London Assembly figures, in April there were 2,595 authorised firearm officers in the Met Police.
It is a figure which has steadily decreased every year since 2018 when there were 2,841 licenced to carry a gun.
Announcing the review, Home Secretary Suella Braverman said the public “depend on our brave firearms officers to protect us”.
“In the interest of public safety they have to make split-second decisions under extraordinary pressures.”
She said that officers have her “full backing”.
“I will do everything in my power to support them,” she added.
In his letter to the home secretary, the Met Police commissioner said that a system where officers are investigated for “safely pursuing suspects” should not have been allowed to develop.
Sir Mark said he would “make no comment” on any ongoing legal matters, but “the issues raised in this letter go back further”.
He said firearms officers are concerned that they will face years of legal proceedings, “even if they stick to the tactics and training they have been given”.
Previous reviews have not delivered change, he added.
“Officers need sufficient legal protection to enable them to do their job and keep the public safe, and the confidence that it will be applied consistently and without fear or favour,” he wrote.
But in instances where officers act improperly, Sir Mark said the system “needs to move swiftly” rather than “tying itself in knots pursuing good officers through multiple legal processes”.
Former Greater Manchester Police chief constable Sir Peter Fahy said any review would “not be wide enough”, adding he believed there are issues around morale and how police prevent organised crime.
BBC/Taiwo Akinola