Sarah Palin, John McCain’s running mate, unlawfully abused her power as Alaska’s governor by trying to have her former brother-in-law fired as a state trooper, according to an ethics investigation released last night. It deals a significant blow to an already embattled Republican ticket just over three weeks until Election Day.

The report, released after a two month investigation, found that Mrs Palin was motivated in part by a personal grudge when she fired Walt Monegan, the police chief, after he failed to dismiss her brother-in-law, who had been involved in an ugly divorce from her sister.

The finding will be an unwelcome distraction for Mr McCain at a time when he is struggling to hold ground against his Democratic rival Barack Obama, who has been boosted by the economic crisis, an issue where significantly more voters trust him on.

Mrs Palin has always maintained that she dismissed Mr Monegan over budget disputes, but the investigator hired by a 14-member bipartisan panel of the Alaskan state legislature concluded that a personal grudge influenced her decision - although it was not the sole reason for her motive to fire him.

Mr Monegan triggered the enquiry this summer when he alleged he had been fired by Mrs Palin, the Governor of Alaska, because he refused to bow to pressure by her, her husband Todd, and members of her staff to sack Mike Wooten, Mrs Palin’s former brother-in-law.

Mr Wooten, an Alaskan state trooper, was divorced from Mrs Palin’s sister in unseemly circumstances. He has not denied tasering his 10-year-old stepson - although he says the boy requested it - and at the height of intra-family conflict the Palins allege that he threatened to kill Mrs Palin’s father.

“I feel vindicated,,“ Mr Monegan said. “It sounds like they've validated my belief and opinions. And that tells me I'm not totally out in left field.”

Stephen Blanchflower, the investigator hired by the legislative committee to conduct the investigation, said he found Mrs Palin in violation of a state ethics law that prohibits public officials from using their office for personal gain. He said she violated a statute of the Alaska Executive Branch Ethics Act.

“Governor Palin knowingly permitted a situation to continue where impermissible pressure was placed on several subordinates in order to advance a personal agenda, to wit: To get Trooper Michael Wooten fired," he said.

The nearly 300-page report does not recommend sanctions or a criminal investigation, but it will inevitably be seized upon by Democrats to undermine both Mrs Palin and Mr McCain, who knew about the ethics investigation before he chose her as his running mate.

The report detailed the unusually high level of access Mrs Palin's husband, Todd, had to her top aides.

In sworn affidavits released yesterday, the man she calls 'The First Dude of Alaska' attempted to shoulder much of the blame for the pressure on Mr Monegan to fire Trooper Wooten.

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