John McCain's running mate Sarah Palin unlawfully abused her power as Alaska's governor by trying to have her former brother-in-law fired as a state trooper, US officials said.
Stephen Branchflower, the chief investigator of an Alaska legislative panel, found Mrs Palin in violation of a state ethics law that prohibits public officials from using their office for personal gain.
The politically charged inquiry imperilled her reputation as a reformer on the Republican presidential ticket.
The inquiry looked into the so-called Troopergate scandal, the dismissal of Alaska's public safety commissioner Walter Monegan who allegedly refused to fire Mrs Palin's brother-in-law Mike Wooten, an Alaskan state trooper, following a messy divorce from her sister.
Mrs Palin has said Mr Monegan was fired as part of a legitimate budget dispute.
The panel found Mrs Palin let the family grudge influence her decision-making even if it was not the sole reason Mr Monegan was dismissed.
"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."
Mr Branchflower said the Republican vice presidential nominee violated a statute of the Alaska Executive Branch Ethics Act.
Mrs Palin and Mr McCain's supporters had hoped the inquiry's finding would be delayed until after the presidential election on November 4 to spare her any embarrassment and to put aside an enduring distraction in an uphill contest against their Democratic rival Barack Obama.
But the bipartisan panel voted to release the report late last night, but not without dissent.
Alaska senator Gary Stevens, a Republican member of the panel, said: "I think there are some problems in this report.
"I would encourage people to be very cautious, to look at this with a jaundiced eye."
The nearly 300-page report did not recommend sanctions or a criminal investigation.
"I find that Governor Sarah Palin abused her power by violating Alaska Statute 39.52.110 (a) of the Alaska Executive Branch Ethics Act," Mr Branchflower said in the 267-page report.
"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."
Mr Monegan's refusal to fire Mr Wooten was not the sole reason he was dismissed but was likely a contributing factor, the report found.
Mrs Palin also allowed her husband, Todd, the so-called first dude of Alaska, to use the governor's office and resources to continue to contact state employees to find some way to get Mr Wooten fired, according to the report.
Meg Stapleton, a spokeswoman for the McCain-Palin campaign, said the report showed Mrs Palin "acted within her proper and lawful authority in the reassignment of Walt Monegan".
"The report also illustrates what we've known all along: this was a partisan led inquiry run by Obama supporters and the Palins were completely justified in their concern regarding Trooper Wooten given his violent and rogue behaviour she said.
"Lacking evidence to support the original Monegan allegation, the Legislative Council seriously overreached, making a tortured argument to find fault without basis in law or fact.
"The governor is looking forward to co-operating with the Personnel Board and continuing her conversation with the American people regarding the important issues facing the country."
Earlier this week, Mr McCain's campaign sought to pre-empt the report by releasing its own analysis which attributed Mr Monegan's firing to a legitimate dispute over budget priorities and control over the department.
They contended that Mr Monegan repeatedly tried to circumvent the governor and her top aides.
"It's not a legal matter as much as a political issue, a management issue, management of her staff," said Thomas Van Flein, a lawyer hired by Mrs Palin to represent her in the matter.