Suella Braverman has said armed police must not fear “ending up in the dock for carrying out their duties” after a marksman was charged with murder.
The home secretary ordered a review into armed policing after dozens of officers in London handed in their weapons, saying they were worried about the murder charge.
Unarmed Chris Kaba, 24, died after he was shot in south London last year.
A Metropolitan Police officer appeared in court on Thursday.
Ms Braverman said on Sunday that officers have to make “split-second decisions” and risk “their lives to keep us safe”.
The Met said many firearms officers were “worried” about how the charging decision “impacts on them”.
A source suggested that more than 100 officers have handed in what is known as a ticket permitting them to carry firearms.
Armed officers from other forces are being deployed as a contingency measure.
The force said its own officers still make up the vast majority of armed police in the capital, but they were being supported from Saturday evening by a limited number of firearms officers from neighbouring forces.
Ms Braverman said: “We depend on our brave firearms officers to protect us from the most dangerous and violent in society.
“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.