John McCain's US presidential campaign last night accused America's news media of orchestrating a scandal to destroy the party's first female vice-presidential candidate, Alaskan governor Sarah Palin.

As Mrs Palin prepared to make the speech of her life addressing a national television audience at the Republican convention, the McCain campaign said the media was orchestrating a scandal to destroy the party's first female vice presidential candidate.

The controversy over aspects of her personal life and her selection as Mr McCain's running mate is a "faux media scandal designed to destroy the first female Republican nominee" for vice-president, his campaign said.

The 44-year-old governor and surprise choice to be Mr McCain's running mate has been under the spotlight in recent days after disclosures that she faces an ethics investigation and that her unmarried 17-year-old daughter was pregnant. For an America that knew little of her, a speech on the third day of the Republican National Convention offered a chance to shift the focus other matters.

She had been preparing for last night's address with McCain aides. "This speech is about a record of reform, her case for Senator McCain's election and a close-up look at an individual with both hands on the steering wheel of America's energy economy," aide Tucker Eskew said.

But questions have arisen about her efforts as mayor of the small town of Wasilla, Alaska, to gain millions of dollars in federal funding - which appears to be at odds with the McCain message of fiscal reform and raised criticism that McCain's campaign had not fully explored her background.

The campaign called on the media to lay off attention paid to her personal life, with a senior campaign adviser decrying the coverage of the story. "This nonsense is over," Steve Schmidt declared in a written statement.

Since her selection as Mr McCain's running mate on Friday, she has been out of sight "working on her speech" but at the centre of a political storm which has raised serious questions about Mr McCain's judgment.

The Arizona senator cancelled an appearance on CNN on Tuesday after tough questioning of his campaign spokesman Tucker Bounds on Monday night revealed he could not point to a single specific example of Mrs Palin's experience.

It has also been reported that she may have only travelled abroad on two occasions - once last year to Germany and Kuwait to visit Alaska National Guard troops and once to Ireland.

Last night, Mrs Palin was hailed as a leader who had the experience and judgment necessary to be Mr McCain's running mate by a series of top Republicans - including President George Bush.

Former Law & Order actor Fred Thompson, who dropped out of the presidential race earlier this year, told delegates at the convention in St Paul, Minnesota: "Some Washington pundits and media big-shots are in a frenzy over the selection of a woman who has actually governed rather than just talked a good game on the Sunday talk shows and hit the Washington cocktail circuit."

Mr McCain yesterday arrived in Minnesota, his first appearance since the event began on Monday.

He was met by Mrs Palin, among others, and shared a hug with his running mate, greeted her daughter, Bristol, and her boyfriend, 18-year-old Levi Johnston. Bristol is five months pregnant and plans to marry her boyfriend.

Mr McCain has been extolled as a war hero and political maverick, with President George W Bush declaring on a video link from Washington that the veteran lawmaker is "ready to lead this nation".

His address marked a diminished role from plans to have him address the convention on Monday, in the prestigious final slot - with polls making it clear Americans want change.