Jürgen Todenhöfer, pictured, spent ten days with the Isis terror group researching his book on the organisation

Islamic terrorists Isis want to wipe the west off the face of the earth with a nuclear holocaust according to a journalist who spent ten days with the group while researching a book.

The terror group allowed Jürgen Todenhöfer to embed with the group because he has been a high-profile critic of US policy in the Middle East.

The German journalist claimed the terror group wants to launch a 'nuclear tsunami' against the west and anyone else that opposes their plans for an Islamic caliphate.

The 75-year-old former German MP wrote up his findings in a new book 'Inside IS - Ten Days In The Islamic State'.

He said that upon his arrival in ISIS controlled territory, that he and his son were forced to hand over their mobile phones to their hosts.

He said he spent several months talking to the terror organisation over Skype before he was allowed to travel into their area.

He told Allan Hall in The Express: 'Of course I'd seen the terrible, brutal beheading videos and it was of course after seeing this in the last few months that caused me the greatest concern in my negotiations to ensure how I can avoid this. Anyway, I made my will before I left.

'People there live in shellholes, in barracks, in bombed-out houses. I slept on the floor, if I was lucky on a plastic mattress. I had a suitcase and a backpack, a sleeping bag.'

Mr Todenhöfer said Isis uses its beheading videos to instill terror into the civilian population in order to make it easier for them to take an area under control.'

Mr Todenhöfer warned that ISIS were the most dangerous terror organisation he ever witnessed.

'I don't see anyone who has a real chance to stop them. Only Arabs can stop IS. I came back very pessimistic.'

He warned that the terror organisation is far more 'dangerous and organised' than people in the West realises.

He said the West has 'no concept of the threat it faces' from the Islamic State and has underestimated the risk posed by ISIS 'dramatically'.

The German reporter spent most of his time in Mosul in northern Iraq, but he also traveled to the ISIS-controlled territories of Raqqa and Deir ez-Zor in Syria.

He added: 'They are extremely brutal. Not just head-cutting. I'm talking about the strategy of religious cleansing. That's their official philosophy. They are talking about 500 million people who have to die.'

Scroll down for video

Mr Todenhöfer said Isis, pictured, were the most 'brutal and dangerous' enemy he has ever seen

He claimed the terror group would try and wipe out hundreds of millions of people if they had the chance

He went on to say that ISIS are 'completely sure they will win this fight'.

In a stark warning issued in a detailed post on Facebook, the journalist wrote in German: 'The West underestimated the risk posed by IS dramatically.

'The IS fighters are much smarter and more dangerous than our leaders believe. In the Islamic State, there is an almost palpable enthusiasm and confidence of victory, which I have not seen in many war zones.'

Mr Todenhöfer went on to say that ISIS have plans for mass genocide, with the aim or eradicating all atheists and religions that are not 'people of the book' or who do not subscribe to their particular brand of Islam.

'The IS want to kill... all non-believers and apostates and enslave their women and children. All Shiites, Yazidi, Hindus, atheists and polytheists should be killed,' he wrote.

'Hundreds of millions of people are to be eliminated in the course of this religious 'cleansing'.

'All moderate Muslims who promote democracy, should be killed. Because, from the IS perspective, they promote human laws over the laws of God.

'This also applies to - after a successful conquest - the democratically-minded Muslims in the Western world.'

The reporter describes the Islamic State is currently operating as a functioning totalitarian state - one which, he claims, many Sunni residents in Mosul are unopposed to since it is preferable to the oppression they suffered under the previous regime.

He told German television that ISIS wants to 'conquer the world'.