Isis has used the latest issue of its propaganda magazine Dabiq to suggest the group is expanding so rapidly it could buy its first nuclear weapon within a year.

The hyperbolic article, which the group attributes to the British hostage John Cantlie, claims Isis has transcended its roots as “the most explosive Islamic ‘group’ in the modern world” to evolve into “the most explosive Islamic movement the modern world has ever seen” in less than twelve months.

Photojournalist John Cantlie is regularly used in the terror group’s propaganda and has appeared in a number of videos, including a YouTube series called "Lend Me Your Ears". He has been held a hostage by Isis for more than two years.

The piece, entitled "The Perfect Storm", describes militant Islamist groups such as Boko Haram, which recently pledged allegiance to Isis, uniting across the Middle East, Africa and Asia to create one global movement.

The article claims this alignment of groups has happened because Isis militants seized “tanks, rocket launchers, missile systems, anti-aircraft systems,” before turning to more extreme weapons the group is not in possession of - such as nuclear weapons.

“Let me throw a hypothetical operation onto the table,” the article continues. “The Islamic State has billions of dollars in the bank, so they call on their wilāyah in Pakistan to purchase a nuclear device through weapons dealers with links to corrupt officials in the region."

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It admits that such a scenario is “far-fetched” but warns: “It’s the sum of all fears for Western intelligence agencies and it’s infinitely more possible today than it was just one year ago.

"And if not a nuke, what about a few thousand tons of ammonium nitrate explosive? That’s easy enough to make."

An attack launched by Isis against America would ridicule "the attacks of the past".

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"They’ll [Isis] be looking to do something big, something that would make any past operation look like a squirrel shoot, and the more groups that pledge allegiance the more possible it becomes to pull off something truly epic.

“Remember, all of this has happened in less than a year. How more dangerous will be the lines of communication and supply a year on from today?”

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The capacity of Isis to acquire such a device is certainly beyond the group at the moment.

The finances of the group have been estimated by some to be in the $2bn area, though it is impossible to verify how much money it actually has access to.

In September last year, the Home Secretary, Theresa May, warned that the militant group could become the world's first "truly terrorist state".

“We will see the risk, often prophesied but thank God not yet fulfilled, that with the capability of a state behind them, the terrorists will acquire chemical, biological or even nuclear weapons to attack us," she said.