A former MI6 spy has claimed a new 9/11 or 7/7 attack could come at any time due to the presence of 'hundreds' of potential Al-Qaida sleeper agents living in the UK.

Aimen Dean, a former member of Al-Qaida who spent eight years working in the Secret Intelligence Service (SIS) gathering vital intelligence for MI5 and MI6, says the biggest threat to the west is the spread of Islamic extremism and Iranian influence.

'It's not about if another 9/11 or 7/7 attack will happen; it's about when,' he told the Sun.

Mr Dean's risky work while a member of the terror group helped to foil significant Al-Qaida terror plots, including one that would have targeted passengers on the subway in New York.

Now he has shared his concerns that there could be 'hundreds' of sleeper members of the organisation in the UK and that the west is wrongly focussing on Russia as the number one enemy.

Mr Dean claims it is Iran that should be the focus of government policy in order to protect the British people.

He says the country was responsible for 'hosting' Al-Qaida for 25 years, opening up opportunities for so-called 'sleeper cells' to carry out attacks on British nationals, including fatal assaults on Brits in the UAE. 

'Unfortunately, I would love to tell you the world is an amazing place, but it's not,' Mr Dean said.

Aimen Dean, a former member of Al-Qaida who spent eight years working in the Secret Intelligence Service (SIS) gathering vital intelligence for MI5and MI6, says the biggest threat to the west is the spread of Islamic extremism and Iranian influence

He has claimed that it is a matter of 'when' another attack such as 9/11 (pictured) or the 7/7 bombings happens and that there are 'hundreds' of Al-Qaida sleeper agents in the UK

'A threat like Iran needs to be countered because of the fact that they are a nation that has sponsored terrorism.'

He is predicting more 'lone-wolf' style attacks in the future and says that although it is 'impossible' to estimate exactly how many potential Al-Qaida members are in the UK, it is at least 'hundreds'.

Mr Dean argues these sleeper agents could be utilised to carry out a terror attack at any time. 

The father-of-one was 17 when he met Khalid Sheikh Mohammed, the mastermind behind the 9/11 attacks, after spending a year fighting in the Bosnian war.

At 18, he travelled to the mountains in Afghanistan where he spent 11 months learning how to build bombs. Mr Dean told how as a self-confessed 'nerd', the mathematical side to the process appealed to him.