Vice-presidential candidate Sarah Palin has criticised Barack Obama in an address to the Republican Convention.

The Alaska governor, who accepted presidential candidate John McCain's nomination to be his running mate, said Mr Obama was using his Change message to make a political career.

"In politics, there are some candidates who use change to promote their careers. And then there are those, like John McCain, who use their careers to promote change in politics."

"I guess a small-town mayor is sort of like a community organiser except that you have actual responsibilities," she said, referring to the Illinois senator's one-time role as a community organiser in Chicago.

Ms Palin and her family have been under intense media scrutiny ever since McCain picked her as running mate.

Revelations that her 17-year-old daughter, Bristol is pregnant rocked the Republican campaign. She has said that Bristol will keep the child and get married to its father. Bristol's boyfriend, Levi Johnston, sat with the family.

She told the delegates: "Our family has the same ups and downs as any other; the same challenges and the same joys."

Ms Palin, 44, praised McCain as the right man to occupy the White House after the November elections

"McCain is a man who wore the uniform of this country for 22 years, and refused to break faith with those troops in Iraq who have now brought victory within sight. And as the mother of one of those troops, that is exactly the kind of man I want as commander-in- chief," she said.

Addressing the delegates earlier, former New York Mayor Rudy Giuliani said of Mr Obama: "He has never run a city, never run a state, never run a business, never run a military unit. He's never had to lead people in crisis."

"This is not a personal attack; it is a statement of fact, he (Obama) has never led anything. Nothing"

Mr McCain will make his acceptance speech at the Convention on Thursday night (Friday morning, Kenya time.)