The Pakistani cricketing legend and politician talks about his country's damaging relationship with the US, how aid and corruption are further ruining it – and how he is sure he will be its next president

When Barack Obama announced in May that American commandos had killed Osama bin Laden in Abbottabad, Imran Khan was furious. "The whole of Pakistan felt this way. Wherever I went I felt this humiliation and anger in people. It was humiliating because an American president announces it, not our president. And because it was the American military, not our military, which this country has given great sacrifices to nurture, that killed him."

Khan stirs his cappuccino angrily. "Most humiliating of all was that the CIA chief Panetta says that the Pakistan government was either incompetent or complicit. Complicit!" But surely Leon Panetta had a point, didn't he? The world's most wanted man was living a mile from Pakistan's military academy, not in some obscure cave. "They're talking about a country in which 35,000 people have died during a war that had nothing to do with us. Ours is perhaps the only country in history that keeps getting bombed, through drone attacks, by our ally."

Khan's rage is directed not chiefly at Obama's administration but at successive Pakistani governments for entrapping his homeland in a dismal cycle of immiseration and mass deaths for the past eight years by supporting the war on terror in return for billions of dollars of financial aid. The manner of Bin Laden's killing and the national shame of its aftermath typify for Khan how Pakistan has never properly learned to stand on its own two feet. He calls it an era of neocolonialism in which Pakistan's people seem destined to suffer as much as, if not more than, they did during British colonial rule.

"According to the government economic survey in Pakistan, $70bn has been lost to the economy because of this war. Total aid has been barely $20bn. Aid has gone to the ruling elite, while the people have lost $70bn. We have lost 35,000 lives and as many maimed – and then to be said to be complicit. The shame of it!"

Arguably Khan is benefiting from that anger. The legendary cricketer turned politician hopes – even expects – to become Pakistan's next prime minister. "Every poll has shown the gap widening between us and other parties." He is modest about his impact on the polls: "It's not what I have done, it's that they have got discredited. These are the best of times and the worst of times. The best of it is that people are hungry for a change."

I sip the tea that his ex-wife, Jemima Khan née Goldsmith, has just handed me. We're sitting on huge sofas in the vast living room-cum-kitchen of her opulent west London home. He's here to see his two sons, Sulaiman Isa, 14, and Kasim 12, who live with their mother, when they return from school. Later this evening he will fly home to Islamabad.

Jemima retreats upstairs so that her ex and I can analyse what went wrong with his country – and the couple's marriage. Understandably, Khan would rather talk about the former.

He recalls his greatest cricketing achievement as Pakistani team captain, winning the 1992 World Cup. Perhaps the 2012 Pakistani election will eclipse that triumph. "I played five World Cups and it was only in the last World Cup before we won [in 1992] that I said: 'Put money on us.' Now I'm saying my party will win. I'm throwing everyone a challenge that nothing can stop this party. Nothing."

Perhaps. But Pakistani politics, to hear Khan talk, isn't cricket. "To have a senior post in the government, you have to have a criminal record." I laugh. Surely not? He names ministers who have. This was one consequence of ex-president Pervez Musharraf's 2007 National Conciliation Ordinance that gave amnesties to many politicians (including former Pakistani prime minister Benazir Bhutto, who returned to Pakistan as a result and was shortly afterwards assassinated). "He did the greatest disservice to us by that ordinance. And guess what – it was brokered by the Bush administration.

"My country can barely stoop any lower. All you need to do with a senior politician today is look at his assets before he came into politics and look at them after and you know why they're there. My party is made up of people who don't need politics. You need people who don't need politics to make money." But surely that implies government by gentry, by people who are independently wealthy? "Or people who are not necessarily wealthy but who are in a profession and are doing quite well out of it outside politics. Career politicians have destroyed our country."

I take a sidelong glance at Imran Khan. He's a young, fit-looking 58, dressed in western playboy uniform (jeans, sports jacket, big-collared open-neck shirt), but with an imposingly stern face that he may have inherited from the Pashtun ancestors on his mother's side of the family. He claims to be shy and introverted, but to me he conveys the enviably easy assuredness typical of English public schoolboys. Indeed, Khan is steeped in that ethos: he was educated at Aitchison College in Lahore, a so-called English-medium school, before being sent to England to study at the Royal Grammar School, Worcester, and then read philosophy, politics and economics at Oxford. Ironically, one of his party's policies is that elite schools such as Aitchison should be abolished for being inegalitarian.

If this cricketing legend did become Pakistan's prime minister, it would involve a remarkable turn around in fortunes. In his early test-cricketing days, he was called Imran Khan't – and that nickname applied too to his political career. Ever since he established his political party Tehreek-e-Insaf (Movement for Justice) in 1996, Khan has fared abysmally. Even the Guardian's Declan Walsh described him in 2005 as making a "miserable politician. Khan's ideas and affiliations since entering politics in 1996 have swerved and skidded like a rickshaw in a rain shower."

Khan may have been a brilliant cricketer who for 21 years until retirement in 1992 made Pakistan a leading force in the international game. He may have once been renowned as a soigné habitué of toff nightclubs such as Annabel's and Tramp in the 1980s, and as the playboy who romanced debutantes Susannah Constantine, Lady Liza Campbell and the artist Emma Sergeant. But is he really the man to lead Pakistan from what he calls "the the edge of collapse"?

He, at least, thinks so. "The old parties are all petrified of me now. They all want to make alliances with me and I say: 'No, I'm going to fight all of you together because you're all the same.'"

Excellent. But how does he propose to effect what he calls a soft revolution in Pakistan? "Oh hawk," he replies unexpectedly, "death is better than that livelihood that stops you ascending." He is quoting a verse from his favourite poet and philosopher, Allama Muhammad Iqbal, who died in 1938 and so missed both Pakistan's birth, its rule by dicators and corrupt dynasties, and its current ignominy.

How do Iqbal's words apply to modern Pakistan? "I take them to mean anything that comes with strings attached damages your self-esteem and self-respect – you'd better die than take it," says Khan. "A country that relies on aid? Death is better than that. It stops you from achieving your potential, just as colonialism did. Aid is humiliating. Every country I know that has had IMF or World Bank programmes has only impoverished the poor and enriched the rich." And American aid, he argues, has had a calamitous effect on his homeland.

What Khan is planning politically echoes what he did in cricket. "Colonialism deprives you of your self-esteem and to get it back you have to fight to redress the balance," he says. "I know for myself and my contemporaries Viv Richards [the great West Indies batsman] and Sunil Gavaskar [the no-less-great Indian batsman] beating the English at cricket was a means of doing that. We wanted to assert our equality on the cricket field against our colonial masters."

Isn't cutting foreign aid a perilous policy for a bankrupt economy? "But it doesn't matter," retorts Khan. "We will cut down expenditure, tax the rich and fight corruption. The reason we're bankrupt is because of corruption. Asif Ali Zardari [Pakistan's current president] puts his cronies on top and they literally siphon off money."

He argues that if Pakistan's two greatest problems, corruption and tax evasion, can be solved, then the country will become solvent. "We have the lowest tax-GDP ratio in the world: 9%. If we get it to 18%, which is India, we're solvent." Not only does Khan believe he can tax the rich but also that exploiting Pakistan's huge mineral reserves will help the country escape its current mess. "A country that has no power is sitting on the biggest coal reserves in the world!"

Tehreek-e-Insaaf's other key policy is withdrawing from the war on terror. Why? "The war on terror is the most insane and immoral war of all time. The Americans are doing what they did in Vietnam, bombing villages. But how can a civilised nation do this? How can you can eliminate suspects, their wives, their children, their families, their neighbours? How can you justify this?

"When I came here at 18 I learned about western rule of law and human rights, innocent until proven guilty. The Americans are violating all of this."

Khan wrote an open letter to Obama arguing that the war was unwinnable. "I said you do not have to own Bush's war – you can't win it anyway. It's creating radicals. The more you kill, the more you create extremism."

Why can't the war be won? "The Soviets killed more than a million people in Afghanistan. They were fighting more at the end than the beginning. So clearly a population of 15 million could take a million dead and still keep fighting. They [the Americans] are going to have to kill a lot of people to make any impact and they also have in Zardari an impotent puppet as Pakistani president who has not delivered anything to the Americans.

"The Americans also don't realise that this whole Arab spring was against puppets or dictators. People want democracy. So this whole idea of planting your own man there, a dictator – neocolonialism is what it's called – is not going to work any more.

"The aid to our puppet government from the US is destroying our country. We're basically using our army to kill our own people with American money. We have to separate from the US."

Khan knows what it is to be attacked from both sides. "I've been called Taliban Khan for supporting the tribal Pashtuns and I've been called part of a Jewish conspiracy to take over Pakistan. I am of course neither."

The latter allegation came when Khan married Jemima Goldsmith in 1995. In a chapter on his marriage in his excellent new book Pakistan: A Personal History, he recalls that, when he left for England aged 18, his mother's last words were: "Don't bring back an English wife." But after his mother's death, Khan did that, even though the British press wailed that Jemima would not be allowed to drive in Pakistan and that she would have to be veiled from head to toe; even though the Pakistani media portrayed the marriage as a Zionist plot to take over Pakistan. No matter, as Khan writes, that his wife wasn't actually Jewish (her paternal grandfather was Jewish), but had been baptised and confirmed as a Protestant. No matter that she converted to Islam and set about learning Urdu on her arrival in Pakistan.

The smears got worse a year after their marriage when Khan launched his political career. "Cross-cultural marriage is difficult, especially when one person has to live in another country. But I thought there was a very good chance of it working because people grow together if they have a common passion. But from the moment my opponents attacked her in the first election in terms of a Zionist conspiracy we had to then take her away from politics. That meant we were doing different things. We couldn't share our passions."

Jemima returned to England, ostensibly for a year to do a masters in modern trends in Islam, taking her sons with her. She never returned, the couple divorced in 2004 and she is now associate editor of the Independent and editor-at-large for Vanity Fair. They remain on friendly terms. "It was very painful that it didn't work out but that bitterness and anger that comes when a marriage breaks down through infidelity was not there. We were completely faithful to each other."

There was no way he could have moved to London? "London is like a second home, but never could I imagine living away from Pakistan." It must be tough with his sons living half a world away most of the year. "Very tough. Nothing gave me more happiness than fatherhood. And here's someone who had great highs in his life. The biggest void in my life is not being close to my children all the time, but mercifully, thanks to my relationship with Jemima, I see them a great deal."

One way of looking at his failed marriage, then, is that it could not survive the bearpit of Pakistani politics. How could he continue in that grim game given the high cost it extorted from you? "Ever since my mother died in great pain from cancer, I have had a social conscience that can only express itself in getting involved in politics. As long as I played cricket there was hardly any social conscience. It came because of my mother and how she was treated." It also came after a spiritual awakening and renewed Islamic faith, in which Iqbal's writings played an important role.

"The No1 thing that struck me about your country when I came here was your welfare state, which I'm sad to say they are dismantling – a big mistake. I thought: 'What a civilised society.' When my mother was treated here we were paying for her and there was a national health patient next to her – equal treatment. We didn't have that in Pakistan."

After his mother's death he founded the Shaukat Khanum Memorial Cancer Hospital and Research Centre in Lahore in her name. "My hospital is the only one in Pakistan where doctors are not allowed to know which patients are paying and which are free. Equal treatment for rich and poor is essential."

But the hospital was only possible because of donations that he raised from the streets of Pakistan's cities. "We needed $4m for the hospital and we had run out of steam so someone suggested we just go out into the streets. I ended up covering 29 cities in six weeks and I just went into the street with a big collecting sack. Only in Pakistan would this happen."

But that Pakistani generosity, he realises, articulates an important principle of Islam, of doing good deeds to get to heaven. In the book he writes that he asked why poor people would give such high proportions of their income to a cancer hospital not even in their own town. "It was always the same reply, 'I am not doing you a favour. I am doing it to invest in my Hereafter.'"

That geneoristy proved a catalyst for Khan's political career, he writes: "I started thinking that these people were capable of great sacrifice. Could these people not be mobilised to fight to save our ever-deteriorating country?" He may have a sentimental vision of poor Pakistanis but Khan has no doubt: they will revolutionise Pakistan, led by him.

Just before I leave him to his children, he tells me that the nadir for Pakistan came last year when Angelina Jolie visited Pakistan's flood-hit area. "It's so shameful. The prime minister gave her a reception in his palace and she commented on its opulence. The prime minister gets his family in a private jet to see her, the family give her expensive presents and yet there are people dying in these flood-affected areas. They were living like Mughal emperors in splendour and our people were dying. It took a Hollywood star to point this out. Our politics can never be so shameful again." That remains to be seen.