The Islamic State terror group wants to carry out a mass casualty attack in Britain and has "no moral barrier" to using chemical weapons, a minister has warned.
Security minister Ben Wallace said there were reports of IS using chemical weapons in Syria and Iraq, where it controls large areas, and that the Moroccan authorities apprehended a cell in February which was harbouring substances that could be used to either make a bomb or a "deadly toxin".
He also pointed to a recent Europol report which warned of the chemical threat and the potential realisation of "everybody's worst fear".
Mr Wallace told the Press Association: "Experts have warned that their ambition is a mass casualty attack and they have no moral barrier to using whatever means possible."
It came after he told the Sunday Times: "The ambition of IS or Daesh is definitely mass casualty attacks. They want to harm as many people as possible and terrorise as many people as possible.
"They have no moral objection to using chemical weapons against populations and if they could, they would in this country.
"The casualty figures which could be involved would be everybody's worst fear.
"We have certainly seen reports of them using it in Syria and Iraq (and) we have certainly seen aspiration for it in Europe."
Mr Wallace also warned about the threat from "the enemy within" as terror groups, Russia and cyber attackers were trying to plant "traitors" in the Government, the military and leading businesses.
"There are traitors. We have to be on our guard for the enemy within," he said.
"The insider threat, as we would call it, is real and it can be exploited and there are people trying to do that as we speak."
The warning comes after a year in which Europe suffered a spate of terror attacks using less sophisticated means.
In two of the most high-profile attacks in Nice and Berlin, lone attackers drove lorries through crowds of people celebrating Bastille Day and browsing a Christmas market respectively. IS claimed responsibility for both attacks.
In March, three co-ordinated suicide bombers attacked the airport and metro system in Brussels, with IS claiming responsibility.