Churches should have a 'bouncer' on the door throughout services to improve security, new counter terrorism advice suggests, as an expert has warned small parish churches are more at risk of attack that larger places of worship.
New guidance issued after the murder of a French priest by Islamic State supporters advises churches should fit CCTV and personal attack alarms.
The risk of a terrorist attack on a church in Britain is believed to have increased since terrorists slit the throat of Father Jacques Hamel.
The draft 12-page guidance drawn up by an adviser to the Home Office says churches should ensure their doors can be securely bolted and recommends worshippers are briefed on what to do if they spot someone suspicious.
It says churches should have "someone on the door of your church welcoming people into the building during service who can close the front door in an emergency. Make sure that someone is stood by the door before, during and after the service, whilst the congregation is present."
The advice says: "The job of the person on the door is to delay any offenders (including those who are not terrorists) so that the police can arrive and deal with them."
It comes as some vicars claim they have been told by church officials not to wear dog collars in public for fear of attracting the attention of would be attackers.
Counter Terrorism Advice for Churches, from National Churchwatch which provides safety and security advice to churches, also advises congregations on what to do if they are at a service which is attacked.
Father Hamel,85, was killed and two nuns were held hostage when two 19-year-old jihadists stormed a church in Saint-Etienne-du-Rouvray, Normandy, during morning mass.
Police urged churches to review their security after the attack in July and the Home Office announced a £2.4m fund to strengthen safety in places of worship
Nick Tolson, director of National Churchwatch, said: "When the French church attack happened, there was a recognition that the risk has increased. The risk is still very low, however, we need to think about what we need to do."
Previous advice written in 2009 was outdated, he said.
He said any attack was likely to target a small parish church, as seen in the French attack.
He said: "It won't be Westminister Abbey or St Paul's, it will be a little church in Bolton or Birmingham. It's the small churches, just like the one in France. You can walk into any church on a Sunday morning and it probably won't be a gun, it will be a knife."
The advice urges all churches to consider fitting CCTV and alarms that can be triggered by clergy or church workers inside.
It also advises that everyone who regularly attends a church "should be briefed on security awareness, and what to do if they see something suspicious".
Mr Tolson, who advises the Home Office's places of worship security committee, said the recent Paris attacks had underlined that people should flee rather than hide in the event of an attack.
He said: "We know now that if you hide for hours, they just walk around and shoot you. The advice is now run and get out of the area."
But he said clergy should continue to wear dog collars.
He said: "We advise them to have their collars on and open their churches because there's zero evidence that wearing collars is any risk."
The Church of England said it had not told vicars to stop wearing dog collars. A spokesman said much of the new security guidance was covered by its own advice, but it was up to individual churches to decide what was appropriate.