Sarah Palin resigned as Governor of Alaska to cash in on the business opportunities presented by her new-found fame, the estranged boyfriend of her eldest daughter said yesterday.

Speculation over the real reasons behind Mrs Palin’s decision to quit has been swirling since her opaque and rambling resignation speech last Friday. A looming scandal, presidential ambitions and the draw of lucrative speaking and writing opportunities have all been cited.

Now Levi Johnston, whose wedding to Bristol Palin, 18, the mother of his infant son, was called off early this year, has told reporters that from what he witnessed while living at the Palin home, the lure of financial enrichment was the most likely explanation.

Mr Johnston, 19, whose relationship with the family has been strained since the break-up, said that he heard Mrs Palin talk on several occasions about her desire to take up some of the deals that she was being offered, including a reality television show and a tell-all book about her life.

“I think the big deal was the book. That was millions of dollars,” Mr Johnston told reporters during a news conference at his lawyer’s office in Anchorage.

Mrs Palin’s lawyers confirmed that she had signed a major book deal with HarperCollins, owned by the same parent company as The Times, but did not disclose how much it was worth. Her lawyers insisted that the book was the only offer that Mrs Palin had taken up.

Mrs Palin’s spokeswoman said: “It is interesting to learn Levi is working on a piece of fiction while honing his acting skills.” Mr Johnston is also pursuing his own book and movie deals based on his liaison with Mrs Palin’s daughter.

Mrs Palin has claimed to be facing outstanding legal fees of $500,000 (£310,000) related to investigations into her affairs and said last week that she was resigning in part to spare the state the cost of defending her against “nuisance” ethics inquiries.

Mrs Palin has attracted at least 19 ethics complaints, ranging from allegations of abuse of office in the dismissal of a state trooper to the filing of expense claims for travel to her home in Wasilla when she refused to live in the state capital of Juneau.

But many pundits, struggling to find a coherent political strategy behind her resignation, have already concluded that financial gain is the most convincing explanation.

As Governor, Mrs Palin earned an annual salary of $125,000 — a figure that, one commentator noted, she could earn in just two weeks as a public speaker.

Mrs Palin’s book deal, believed to be worth several millions of dollars, also offers her the chance to take command of her own narrative, after oft-expressed frustrations over her negative portrayal in the media.

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