Currently the Metropolitan Police have around 2,200 trained marksmen and this is set to rise by 600.
Announcing the plan, Scotland Yard chief Sir Bernard Hogan-Howe said: "In the days following Paris, I asked my firearms team to increase the number of armed response vehicles available on our streets, which we did. Now, I have decided that we take the steps to increase these numbers on a permanent basis."
He said the new officers would "more than double the number of armed response vehicles on our streets".
Pastor Nims Obunge from the Peace Alliance told Premier's News Hour the new officers will need support: "What we need to pray for is that God gives them the wisdom to know when it's right and when it's wrong.
"An innocent life can be lost when it's wrong, but a nation and its people can be saved when it's right."
He stressed it was vital the new armed officers were seen in a way that would not frighten the public.
"Pray that God gives them the courage to do that job because they volunteer to carry that fire arm, it's not imposed on them, it's a decision each officer makes.
"So, we need to pray for that courage and a capacity to do it with a sense of duty."
Mayor of London Boris Johnson said: "Keeping Londoners safe is my number one priority, and, while this city remains one of the safest in the world, the terrible events in Paris last year remind us that we have to be prepared to meet any potential terrorist threat.
"Increasing our armed response capabilities, alongside additional training and support, is absolutely essential, and we welcome the commissioner's announcement today and the funds being made available by the Home Office to support it.
"As a leading world city, London faces unique challenges and a growing population, and it is only right that we ensure the proper level of police protection so we can continue to keep our city safe."
