A Police Federation branch chairman has claimed rural officers fear they would be "sitting ducks" in the event of an armed terrorist attack.
John Apter, head of the Hampshire branch, told the BBC that a national shortage of armed officers could leave police in isolated areas "unarmed and vulnerable".
After the terror attacks in Brussels, the Government announced more firearms officers would be trained.
Speaking to BBC Radio 4´s File on 4, Apter said that there were potential targets in rural and coastal areas - such as energy and power plants - but that armed officers could be more than 70 miles away in an emergency.
"Being realistic, if a firearms unit was coming from the middle of the county you are still talking about 30 miles away - you are not talking about a few minutes," he said.
He said the distance would mean an understandable delay which would be even greater if the officers had to come from as far away as 70 miles.
"So the only officers that you have available are unarmed and vulnerable officers and they are the officers that are saying to me that in a terrorist situation they would be sitting ducks," he added.
His concerns come after new figures released last month showed that the number of firearms officers in England and Wales plunged by nearly a fifth in five years.
Earlier in April, Prime Minister David Cameron announced that more armed officers were to be stationed across the country to deal with a Paris-style attack.
Forces are training around 1,500 extra personnel as part of counter-terrorism efforts, with 400 ready to be deployed to cities outside London around the clock.
Police minister Mike Penning told the BBC that £143 million had been committed over the next five years to provide "a national uplift in armed policing capability".