The former head of Britain’s Armed Forces has blamed David Cameron for the rise of Islamic State, saying he lacked ‘the balls’ to crush them militarily when they first emerged as a threat.

In a scathing attack on Cameron’s record on Libya and Syria, General Sir David Richards, ex-chief of the defence staff, said the Prime Minister was more interested in pursuing a ‘Notting Hill liberal agenda’ than showing serious ‘statecraft’. Richards was backed by Britain’s spy chief, who delivered an astonishing personal slap-down to Cameron in a bitter Downing Street clash over Libya.

The revelations come in an explosive new biography of Cameron by Britain’s leading political biographer Sir Anthony Seldon, which is serialised in The Mail on Sunday starting today.

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Taking different sides: Cameron and Chief of Defence Staff General Sir David Richards in 2010

Seldon’s book, based on unprecedented access to Cameron, George Osborne, fellow Ministers, military and diplomatic chiefs, Downing Street officials and mandarins, provides a dramatic account of behind-the-scenes rows in Cameron’s Government.

The book, Cameron At 10, reveals that:

The Prime Minister was in a bitter feud with Sir David over how to deal with ISIS and over his ‘half-baked’ campaign to oust Libya’s Colonel Gaddafi.

The general was echoed by the then head of MI6 John Sawers who told a shocked Cameron to his face that his plan to attack Libya was not in the ‘national interest’ but was purely for ‘humanitarian reasons’.

Barack Obama repeatedly refused to take Cameron’s calls, leading to a rift between the PM and the President. Cameron regards him as ‘too rational and considered’ and Obama is cruelly nicknamed ‘Spock’ by the Foreign Office.

An extraordinary bid by Tony Blair to arrange a ‘deal’ for Gaddafi to get out of Libya is also revealed by Seldon.

He says the former Prime Minister approached No 10, but the proposal was turned down by Cameron.

Cameron has vehemently defended his decision to lead the attack on Libya, though some experts say the fall of Gaddafi is linked to the huge rise in migrants trying to reach Europe by boat from Libya.

An extraordinary bid by Tony Blair to arrange a ‘deal’ for Gaddafi to get out of Libya is also revealed by Seldon

Critics are divided over whether earlier intervention in Syria would have halted the rise of Islamic State.

Seldon reveals a series of clashes between Cameron and the general over Cameron’s stance on Libya and Syria.

During lengthy interviews with Seldon for the book, Sir David castigates Cameron for failing to back plans for tougher military action when the Syrian crisis erupted in 2012.

The general tells the author: ‘If they had the balls they would have gone through with it… if they’d done what I’d argued, they wouldn’t be where they are with ISIS.’

He adds: ‘In Ukraine, as in Syria and Libya, there is a clear lack of strategy and statecraft. The problem is the inability to think things through. Too often it seems to be more about the Notting Hill liberal agenda rather than statecraft.’

In a showdown over Libya at a meeting of the National Security Council, headed by the PM, Sir David and MI6 chief Sawers challenge him head on.

Told bluntly by Cameron that his call for military action to depose Gaddafi is ‘in the British national interest, speak now or hold your peace’, they take up the gauntlet. Using the most direct language, Sawers delivers an astonishing personal rebuke to the Prime Minister, telling him it has nothing to do with ‘the national interest’ and saying Cameron is acting for ‘humanitarian reasons,’ pointedly drawing attention to the gulf between the two political motives.

Seldon also discloses a series of disputes between Cameron and Osborne. The author suggests Osborne initially resisted Cameron’s plan for an EU referendum because he feared it would damage him if he succeeded Cameron as Prime Minister of a UK that had left EU.

According to the book, Cameron was ‘angry’ with Osborne over the notorious ‘omnishambles’ Budget of 2012 and insisted on a bigger say in future Budgets.

Seldon lifts the lid on new details of personal squabbles between other senior Tories. He says furious Cameron warned Boris Johnson he risked helping Ed Miliband become Prime Minister and told Johnson to ‘f****** shut up’.

And he writes that Osborne regards Theresa May’s leadership ambitions as ‘ludicrous’ as tempers fray over immigration. Seldon and co-author Peter Snowdon do not pull punches.

Seldon writes that Osborne regards Theresa May’s leadership ambitions as ‘ludicrous’ as tempers fray over immigration

They lambast Cameron’s ‘abject judgment’ in ignoring warnings not to appoint former News Of The World editor Andy Coulson, later jailed in the phone hacking trial, as his Downing Street spin doctor.

The book also provides a fresh insight into the dramatic events of Election Day on May 7.

The authors have obtained the contents of a pre-prepared speech conceding defeat to Miliband, delivered by Cameron to tearful Tory aides on the patio of his Oxfordshire home hours before he learned that, in fact, he would be heading back to No 10.

The book is the latest in a series of biographies by Seldon. His accounts of the Premierships of John Major, Tony Blair, Gordon Brown, and now Cameron, have cemented his reputation as the most influential and respected political author in modern times.

Sir Anthony Seldon has had unprecedented access to David Cameron and George Osborne

If Cameron and his Notting Hill liberals had balls they would not be where they are with I.S.

Authoritative yet uncompromisingly tough, Sir Anthony Seldon is our leading political biographer. His books on Major, Blair and Brown have established an unrivalled reputation. Now, with co-author Peter Snowdon, he has had unprecedented access to David Cameron and George Osborne. Today we publish their compelling new biography of the Prime Minister – a gripping and at times astonishing account of the people who rule us…

During the Libyan uprising against Colonel Gaddafi in 2011, David Cameron works particularly closely with his chief of staff, Ed Llewellyn, who could draw on his experience as an adviser to Paddy Ashdown, when he was high representative to Bosnia in the early 2000s.

Cameron is full of zeal: weighing heavily in his mind is the human cost of inaction.

General Sir David Richards, chief of the defence staff, believes Llewellyn is egging on Cameron. He believes they have a model of the Balkans in their heads. By acting now, they think they can prevent another Srebrenica massacre in Benghazi.

The National Security Council, a body set up after the election to co-ordinate defence and security policy, meets daily and a split opens up. Richards and John Sawers, head of MI6, warn of the risks of ‘half-baked’ military intervention. Other NSC members – including Cameron, Nick Clegg and Llewellyn – are all in favour of action.

Some military and intelligence officials believe Cameron’s team are ‘20 years out of date when it comes to dealing with conflict’, having not been immersed in the Iraq and Afghanistan campaigns.

'DAVID WAS JUST ANOTHER TALENTED ETONIAN... UNTIL IVAN' Close bond: Cameron pushes Ivan as he goes shopping with his family in 2006 Cameron’s profoundly disabled son, Ivan, died at the age of six in 2009. Nothing in the Prime Minister’s life has affected him as deeply as the birth, life and death of his son. ‘David was just another talented Etonian until Ivan,’ says Andrew Feldman, chairman of the Conservative Party and one of Cameron’s oldest friends. ‘What Ivan gave him was compassion and humanity,’ says Feldman. Cameron spoke movingly of Ivan in his 2012 conference speech, regarded as one of his best. Feldman takes some credit for persuading him to open up. ‘I’m always telling him to bring out his inner Semite,’ he says, referring to Cameron’s Jewish ancestry (his great-great-grandfather was the Jewish financier Emile Levita), which Feldman thinks explains Cameron’s inner warmth. Advertisement

Cameron becomes impatient with the Whitehall machine. At an NSC meeting in March, he declares that ‘intervention in Libya is in the British national interest, speak now or hold your peace’.

He is confronted by Sawers who tells him bluntly it is not a matter of ‘national interest’ and that Cameron is acting purely for ‘humanitarian reasons’. Cameron is surprised by the challenge, but quickly answers somewhat unsatisfactorily, ‘Yes, yes, but it is important that we do these things.’

It is statements like this that lead many in the intelligence and defence community to worry that the whole situation is ‘not clearly thought through’.

Progress against Gaddafi becomes bogged down and when Benghazi is secure, Richards says hostilities should cease and talks be opened with Gaddafi. Cameron rules out the suggestion.

Richards complains that he is not being listened to. Number 10 suspects he is talking to the press. Cameron’s frustration is rising by the week.

Whitehall is placed on a war footing, and what William Hague dubs the ‘anaconda strategy’ – squeezing Gaddafi to death – is launched.

Number 10 argues that they should be denying oil to forces loyal to Gaddafi, and taking out fuel lines and depots. Cameron agrees.

The military reply is that this is a NATO-led campaign and that these actions are inconsistent with the UN resolution. Cameron is frustrated and in favour of cutting loose from NATO and taking action unilaterally.

Tony Blair telephones Number 10 to say he’s been contacted by a key individual close to Gaddafi, and that the Libyan leader wants to cut a deal with the British. Blair is a respected voice in the building and his suggestion is examined seriously.

Cameron had been repulsed by Blair’s decision to rehabilitate Gaddafi, and as opposition leader had argued strongly in 2009 against the Scottish government’s return of the Lockerbie bomber Abdelbaset al-Megrahi to Libya on the grounds of illness.

Policewoman Yvonne Fletcher was killed by a Libyan outside their embassy in London in 1984, when Cameron was still at Eton. Four years later came the Lockerbie bombing of Pan Am Flight 103 killing 270 people. When the bomb was proven to be planted by a Libyan, Cameron became still more angry.

Gordon Brown claimed the Scottish government took the decision on al-Megrahi. Cameron did not believe him, and once inside Number 10, ordered a review into the episode. It concluded that the previous government ‘did all it could to facilitate’ the release of al-Megrahi’.

Cameron decides not to follow up Blair’s approach regarding a deal with Gaddafi: he wants to avoid doing anything which might be seen to give the Libyan leader succour. Richards’ complaints do not let up: he feels Cameron and the NSC are interfering with the military operation even down to the most tactical level.

Libya is a formative experience for Cameron. Rose-tinted spectacles have been removed from his eyes about fellow world leaders.

He cannot rely on Obama, nor Merkel, and Sarkozy’s ego knows no bounds.

Plan rejected: IS fighters march through the streets in Raqqa, the terrorist group's de facto capital

He is more sceptical of the MoD and the service chiefs than before. At the conclusion of hostilities, in an attempt to show that there are no hard feelings, he presents Richards with a signed photograph, and a first edition of T. E. Lawrence’s book, Seven Pillars of Wisdom.

But it is not the last of their battles. They differ again in 2012, over Syria, when the British military considers using Western ‘boots on the ground’ and air power.

When Richards presents his plan to the NSC, the response from Number 10 is that it would be unsellable to Washington as well as contrary to Parliamentary and public opinion.

Richards says: ‘If they had the balls they would have gone through with it... if they’d done what I argued, they wouldn’t be where they are with ISIS.’

Cameron’s foreign policy is becoming roundly criticised.

To Richards, the reasons are clear: ‘In Ukraine, as in Syria and Libya, there is a lack of strategy and statesmanship.

‘The problem is the inability to think things through. Too often it seems to be more about the Notting Hill liberal agenda rather than statecraft.’