The Christian Police Association (CPA) said marksmen are "crucial" to keeping communities safe, after the Metropolitan Police revealed its additional teams are now ready to operate.
Executive director of the CPA, Lee Russell told Premier having more police officers who carry firearms is just one aspect to consider when tackling terrorism.
He said: "I think it's a very proportionate and pragmatic response by the [Metropolitan Police] commissioner and the Mayor [of London].
"When we look at the threat level where attack is highly likely, I think the commission is trying to protect Londoners and visitors to London; I think it's entirely appropriate."
"The key issue is for communities to work with the police, for us to stand together against any hatred and to let the police know immediately if we see anything suspicious at all."
Metropolitan Police Commissioner Sir Bernard Hogan-Howe said: "The reality of having to deal with armed and deadly attackers is that you need firearms officers who will use force to stop those attackers in their aim.
"Our firearms officers are the ones who will run towards the danger. They are our heroes.
"Despite the fact they are carrying guns, they are still police officers, and I want the public to approach and talk to them - they are out on our streets to reassure and help the public."
Meanwhile, the Police Federation of England and Wales warned that police forces across the two nations are struggling to recruit the right volunteers for their firearms posts.
Chairman Steve White said it may take at least two years to get the extra 1,500 firearms officers planned ready.
Asked whether communities might have concerns about equipping more officers with firearms, Lee Russell added: "Last year, firearms were discharged only seven times in this country.
"Firearms officers are highly trained but they have got a very difficult job to do so you do need to be aware that they may not walk up to you in the same way as an officer who is unarmed."
In addition to the 600 armed officers announced on Wednesday as ready for operations, Scotland Yard plans to put more marksmen on patrol.