Dozens of Metropolitan police firearms officers are refusing to go out on armed patrols after one of their colleagues was charged with murder.
More than 70 police marksmen said they want time to consider whether or not they wish to still carry a gun given their colleague is facing a murder charge.
Others are declining to go out on regular armed patrol and have remained at their stations while others said they will respond only in emergency situations.
It follows the charging of an armed officer, who has only been identified as NX121, with the murder of Chris Kaba in September last year.
Kaba, 24, died in Streatham Hill, south London, after he was shot through a car windscreen during an armed stop.
The officer has been given conditional bail and is expected to stand trial next year.
Before the murder charge last week, only five marksmen, believed to be close colleagues of the accused officer, had handed back their “blue tickets” – so-called because of the size and colour of the individual firearms licence given to trained and authorised officers.
Senior officers, including the Met commissioner, Sir Mark Rowley, have met the firearms teams to discuss the implications of the decision to charge their colleague with murder.
Scotland Yard said: “Senior officers, including the commissioner, have been meeting with firearms officers in recent days as they reflect on the CPS decision to charge NX121 with murder.
“A number of officers have taken the decision to step back from armed duties while they consider their position. That number has increased over the past 48 hours.
“We are in ongoing discussions with those officers to support them and to fully understand the genuinely held concerns that they have.”
The Met has alerted neighbouring forces of the situation and requested help under the mutual aid system if problems arise.
It is understood that firearms cover at airports, royalty and diplomatic protection and at parliament will not be affected.
“The Met has a significant firearms capability and we continue to have armed officers deployed in communities across London as well as at other sites including parliament, diplomatic premises, airports, etc. Our priority is to keep the public safe. We are closely monitoring the situation and are exploring contingency options, should they be required,” said the force.
The situation will be raised with Suella Braverman at a police memorial day ceremony on Sunday in Cardiff to honour officers who have died on duty. The home secretary and her officials are understood to be monitoring developments.
After his meeting with firearms officers, Rowley said: “They were understandably anxious as they consider how others may assess their split-second decisions years after the event, with the luxury of as much time as they want to do this, and the effect this can have on them and their families.
“They are not only prepared to confront the armed and dangerous to protect London’s communities but they do so recognising the uniquely intense and lengthy personal accountability they will face for their split-second operational decisions.
“Indeed, I understand why many of them are reflecting on the potential price of such weighty responsibilities. Bravery comes in many forms.
“When officers have the levels of uncertainty and worry I saw in my colleagues today, simply going in and doing their jobs, not knowing what incidents are ahead of them, is courageous.”
