Julian Assange's publishers will publish on Thursday the "unauthorised first draft" of his autobiography without his consent, months after the WikiLeaks founder withdrew from a million-pound contract for his memoirs.

In a dramatic move, Canongate has defied Assange's wishes and secretly printed thousands of copies of Julian Assange: The Unauthorised Autobiography, with the book being shipped amid strict security to booksellers in preparation for imminent release. The enormous security operation was put in place by the publishers, according to a source, to stop the author blocking publication.

Assange signed a high-profile deal, reportedly worth a total of £930,000, with the Edinburgh-based publisher and the US firm Alfred A Knopf in December. The manuscript was subsequently sold in more than 35 countries. Assange said at the time that he believed the book would become "one of the unifying documents of our generation".

But after seeing a first draft in March, the WikiLeaks founder told his publishers that he no longer intended to write the book, believing it could give ammunition to US prosecutors seeking his extradition over possible espionage charges relating to the WikiLeaks cable release.

He formally withdrew from his contract on 7 June and since then the Australian and his publisher have been locked in a bitter dispute over the contract and his £500,000 advance, which he has not returned. Assange, requiring funds for his legal fight against extradition to Sweden to face allegations of rape and sexual assault, had placed the advance in escrow, meaning that his former legal team have first claim on any assets.

The Independent, which is to serialise the book, starting on Thursday, said Andrew O'Hagan, Assange's ghostwriter, had asked for his name to be removed from the book. The paper said that Canongate, faced with a financial crisis, gave Assange two months to work on the manuscript and, finally, a 12-day window to seek an injunction, which expired on Monday. Assange has not sought to block the book.

Assange did not respond to requests for comment, but according to a source close to him, he was aware the publisher had plans to release the draft manuscript, and would have liked to have enjoined it, "but the manner in which this has happened has reduced his options to do so. The book is not in a form that Julian ever expected or believed should be published, and certainly he's concerned that it isn't something that he has properly read through and checked." Neither O'Hagan, nor Assange's current or former lawyers were available for comment.

Canongate said: "Despite sitting for more than 50 hours of taped interviews and spending many late nights at Ellingham Hall in Norfolk (where he was – and still is – living under house arrest) discussing his life and the work of WikiLeaks with the writer he had enlisted to help him, Julian became increasingly troubled by the thought of publishing an autobiography. After reading the first draft of the book that was delivered to the publishers at the end of March, he declared: 'All memoir is prostitution.' On 7 June 2011, Julian told Canongate he wanted to cancel his contract.

"However, he had already signed his advance over to his lawyers to settle his legal bills and has not repaid the advance owed since. So the contract still stands and Canongate has decided to honour it and publish the autobiography."

In a preface to the book, Canongate explains its reasons for defying Assange's wishes. ""We disagree with Julian's assessment of the book. We believe it explains both the man and his work, underlining his commitment to the truth. Julian always claimed the book was well written; we agree, and this also encouraged us to make the book available to readers." The volume, Canongate said, "fulfils … the promise of the original book proposal and is, like its author, passionate, provocative and opinionated.".

Given sufficient sales, the publisher confirmed Assange would receive royalties once the advance had been covered.

The Independent says Assange writes in the book about Swedish allegations that he had been warned by a source in an unnamed intelligence agency that the US government was planning to set him up.

Speaking of the two women who accused him of assault, he says: "The international situation had me in its grip, and although I had spent time with these women, I wasn't paying enough attention to them, or ringing them back, or able to step out of the zone that came down with all these threats and statements against me in America. One of my mistakes was to expect them to understand this? I wasn't a reliable boyfriend, or even a very courteous sleeping partner, and this began to figure. Unless, of course, the agenda had been rigged from the start."

In the book extracts published on Wednesday, Assange gives his first account of the sexual encounters with the two women in Stockholm which led to the current demands from Swedish authorities for his extradition to answer sexual assault allegations.

The memoirs say Assange describes one of the women, without naming her, as "a little neurotic". He says that he failed to phone the second women after their night together, which "turned out to be the most expensive call I didn't make".

He insists: "I did not rape these women, and cannot imagine anything that happened between us that would make them think so, except malice after the fact, a joint plan to entrap me, or a terrible misunderstanding that was stoked up between them. I maybe a chauvinist pig of some sort, but I am no rapist."

The book says Assange admits one of the women's claims: that they wanted him to take an STD test, which he failed to do. But the book is silent on the main allegation: that he had sex without a condom against his partner's will.

In the extracts, he also talks of the thrill of computer hacking, and how accessing top-secret websites quickly became addictive: "The thrill was exorbitant. It was like the first time you beat an adult at chess."

He writes of himself and other hackers finding their "ways into the workings of vast corporations" and the excitement of the experience as being "mindblowing."

The book will not be published in the US. "We cancelled our contract for Julian Assange's memoir," Knopf told the New York Observer. "The author did not complete … the manuscript or deliver a book to us in accordance with our agreement. We will not be moving forward with our publication."