Britain must stop 'sleepwalking' and prepare to tackle Muslim extremism as seriously as it planned for the Second World War, a former head of the Armed Forces warned.

Lord Richards of Herstmonceux said extremism posed a 'real threat' to the world and condemned politicians for being too 'reluctant' to lead the way.

He warned that Islamic State jihadists would wreak a 'hell of a lot of damage' in the coming years and said they must be defeated through 'effectively military intervention'.

Speaking at the Chalke Valley History Festival, the former Chief of the Defence Staff, said: 'I think the problem is that we have not seen that we need to approach this issue of Muslim extremism as we might approach World War Two back in the 30s.'

Britain must stop 'sleepwalking' and prepare to tackle Muslim extremists like ISIS (file photo) as seriously as it planned for the Second World War, a former head of the Armed Forces warned

He argued the Armed Forces risked being left 'on the back foot' by leaders who fail to plan properly.

He added: 'This is a real threat to us and we're sleepwalking in the way we're approaching it.'

Defence Secretary Michael Fallon has suggested it could take years to defeat Islamic State.

Britain has committed a few hundred troops to training the Kurdish peshmerga and the Iraqi forces.

The UK has also sent warplanes to drop bombs on Islamic State positions.

But militants are still gaining ground in the war-torn regions and Western attempts to stop their advance as a whole have failed.

Lord Richards said: 'We do not have a generation.

'In that generation, even in 10 years, a hell of a lot of damage is going to happen and it will continue to draw all sorts of people into their ranks and get stronger and stronger.

'It needs to be dealt with and it is an existential threat to all of us.'

The UK has so far ruled out boots on the ground in Iraq or Syria, claiming even the Iraqi leader does not wish for it.

Lord Richards (pictured) said extremism posed a 'real threat' to the world and condemned politicians for being too 'reluctant' to lead the way

But military chiefs have said the battle cannot be won from the air and can only be won from the ground.

He said he would be 'most surprised' if Britain did not enter into combat within the next five years, warning Isis must be defeated through 'effectively military intervention'.

Lord Richards, patron of the Armed Forces Muslim Association, added: 'I'm not necessarily advocating the use of a British armoured brigade and all that implies, but it means a much more comprehensive military strategy that will much more quickly deal with Isis.

'If we aren't in combat again within the next five years I will be most surprised.

'And as ever it will be forced onto reluctant politicians, and we'll be forced onto the back foot and not as properly prepared for it as we could be if they took the initiative.' > > During defence talks at Nato in Brussels on Tuesday, leaders said they were planning to return to Iraq in order to fight the Islamic State, four years after leaving the country.

The military alliance will launch a mission to train Iraqi officers as the Baghdad government struggles to defeat the jihadist group.