Republican vice-presidential candidate Sarah Palin speaks during the Republican National Convention in St. Paul, Minn., on Wednesday. (Jae C. Hong/Associated Press)

Republican vice-presidential candidate Sarah Palin accepted her party's nomination for the position to thunderous applause Wednesday, pulling no punches in her rowdy criticism of Barack Obama.

Taking centre stage of the Republican convention in Minneapolis-St. Paul, the Alaska governor, 44, said it would be a privilege to serve alongside John McCain — a Vietnam war veteran she described as "a true profile in courage."

Her words for Obama were less kind.

"Victory in Iraq is finally in sight; he wants to forfeit," she said of the Democratic presidential nominee.

"Al-Qaeda terrorists still plot to inflict catastrophic harm on America; he's worried that someone won't read them their rights.

"Government is too big; he wants to grow it."

On the same day the McCain campaign demanded that the press back off questioning her personal and political background, Palin stood her ground on the convention stage at the Xcel Energy Centre.

"I've learned quickly these last few days that if you're not a member in good standing of the Washington elite, then some in the media consider a candidate unqualified for that reason alone," Palin said.

"But here's a little news flash for all those reporters and commentators: I'm not going to Washington to seek their good opinion. I'm going to Washington to serve the people of this country."

Palin, whose revelation earlier this week about the pregnancy of her 17-year-old daughter sparked a media frenzy, made her case as to why she should be vice-president, citing her record as governor of Alaska and, before that, as a mayor of Wasilla, a town with a population of 6,700.

"Since our opponents in this presidential election seem to look down on that experience, let me explain to them what the job involves," she said in the prepared text of her speech, taking aim at Obama, who worked as a community organizer in Chicago as a young man.

"I guess a small-town mayor is sort of like a 'community organizer,' except that you have actual responsibilities."

Since taking office as governor, Palin said, she had taken on the oil industry, brought the state budget into surplus and vetoed nearly a half billion dollars in wasteful spending.

As she accepted the party's nomination, Palin also spoke humorously about her personal story of being a mother of five, praising her eldest son, Track, 19, who is preparing to deploy to Iraq next week. She also made a tender acknowledgment that "sometimes even the greatest joys bring challenge," referring to her baby Trig, who has Down Syndrome.

Palin delivered her popular 40-minute speech beginning at 10:30 p.m. ET. When it ended, McCain joined Palin on stage along with her family.

"Don't you think we made the right choice for the next vice-president of the United States?" he asked a roaring crowd. "And what a beautiful family."

Palin's address followed a fiery speech by former New York City mayor Rudy Giuliani, who slammed Obama for his lack of experience.

"He is the least experienced candidate for the president of the United States in at least the last 100 years. This is not a personal attack. It's a statement of fact — Barack Obama has never led anything. Nothing. Nada," Giuliani told a screaming crowd.

"Gov. Palin represents a new generation. She's already one of the most successful governors in America and the most popular. And she's already had more executive experience than the entire Democratic ticket combined."

The evening ended with McCain's official nomination for president following a roll-call vote. He is expected to accept the nomination in a speech to be delivered Thursday night.

While his choice of Palin as running mate surprised many, it is said to have rejuvenated elements of the Republican base because of her conservative anti-abortion and pro gun-rights stances.

She has also been hailed as a maverick politician, a term often associated with McCain, for taking on the political establishment, including members of her own party.

McCain campaign fed up

But that message became muddled after it was revealed her unmarried daughter was pregnant. Since then, the pregnancy has become the focus of the media spotlight. Reporters have repeatedly questioned McCain's campaign about the vetting process, since McCain had just met Palin once before he offered her the job.

The McCain campaign has insisted they knew about the pregnancy before Palin was announced as the vice-presidential contender.

On Wednesday, the McCain campaign signalled it was fed up with the repeated media questions about Palin's background, her family and the vetting process.

"This nonsense is over," senior campaign adviser Steve Schmidt said in a written statement. "Her selection came after a six-month-long rigorous vetting process where her extraordinary credentials and exceptionalism became clear.

"This vetting controversy is a faux media scandal designed to destroy the first female Republican nominee for vice-president of the United States, who has never been a part of the old boys network that has come to dominate the news establishment in this country."

But questions have also swirled about her supposed reformist image following reports that Palin sought pork-barrel projects for her city and state.

She also accepted at least $4,500 US in campaign contributions in the same fundraising scheme at the centre of a public corruption scandal that led to the indictment of Alaska Senator Ted Stevens. The contributions were not illegal for her to accept.

A Republican-dominated legislative committee is also investigating whether Palin dismissed Walt Monegan, her state's public safety commissioner, after he allegedly refused to fire a state trooper who had divorced Palin's sister.

With files from the Associated Press