The highest paid staff member on the McCain campaign is Sarah Palin's make-up artist, it emerged today, in a fresh blow to the vice-presidential candidate's image as an average "hockey mom".

Just as Mrs Palin was struggling to defend herself against criticism of her $150,000 wardrobe budget, it was revealed that Amy Strozzi, who once did makeup work on the television show "So You Think You Can Dance?", received $22,800 for the first two weeks of this month, more than the candidate's chief foreign policy adviser, Randy Scheunemann, according to a filing report.

The news could not have come at a worse time for the Alaska governor, as evidence mounts that she has become a significant drag on the Republican ticket.

Mrs Palin insisted today that she is "frugal" as she sought to defend the controversial fashion budget lavished on her since becoming John McCain's running mate.

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The revelation earlier this week of the sum spent in September on clothes, hair and make-up for Mrs Palin and her family - undermining her carefully crafted folksy persona - was part of a set of broader problems now facing the Alaska governor. According to new polls she has become a bigger liability for Mr McCain, 72, than any other factor.

Mrs Palin spoke hours before giving a sworn deposition in the "Troopergate" inquiry, as a second investigation opened into whether she abused her office by trying to get a state policeman fired to settle a personal score. A first report issued earlier this month concluded that she violated ethics laws in attempts to get her former brother-in-law sacked.

A Wall Street Journal/NBC News poll on Wednesday asked voters what concerns them about the Republican ticket, and Mrs Palin was the number one worry for them; 47 per cent had a negative impression of her, while just 38 per cent see her in a positive light.

Her inexperience and faltering responses to foreign policy questions has also helped erase the "Palin bounce" that boosted the ticket in the fortnight after she was chosen: 55 per cent now think she is unqualified to be president, a troublesome number given Mr McCain's age.

In an interview with the Chicago Tribune, Mrs Palin said of the purchases at such exclusive clothes shops as Saks Fifth Avenue and Neiman Marcus: "If people only knew how Todd [her husband] and I and our kids shop so frugally. My favourite shop is a consignment shop in Anchorage, Alaska, called 'Out of the Closet'."

She said of the controversy: "That whole thing is just, bad! What did they say...150 grand? It wasn't anywhere near that. Those are not ours. We give those back, those go to charity or they'll be auctioned off or whatever." She added: "It's kind of painful to be criticised for that, that is not who we are."

Vice-presidential picks rarely have a significant impact on the outcome of presidential races, but Mrs Palin is emerging as an exception. While she has energised the conservative base - a crucial factor for Mr McCain in turn-out-the-vote efforts on Election Day - she is also being cited as a major reason by some prominent Republicans for their defections to Barack Obama.

Colin Powell, President Bush's former Secretary of State, said her unreadiness to be president was a significant factor in his endorsement of the Democrat last week. Ken Adelman, a Republican hawk and former close friend of Dick Cheney who has become disillusioned with the Administration, is backing Mr Obama. He said the choice of Mrs Palin made him switch sides.

Mrs Palin today gave her first major policy speech – on children with special needs – in Pittsburgh, Pennsylvania, a state she and Mr McCain are targeting. Her six-month-old son Trig has Down Syndrome.

Meanwhile the McCain campaign released a new advertisements using the careless remarks of Joe Biden, the Democrat's own running mate, against him. Mr Biden said that an international crisis will be "generated" to test Mr Obama in his first few months in office.

The advertisement says that is "what electing Barack Obama will mean. It doesn't have to happen. Vote McCain."

Mr Obama returns to the campaign trail on Saturday after visiting his gravely ill grandmother in Hawaii. He remains ahead in the polls but warned today that "national polls don't mean anything."

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