Rushdie, a vocal supporter of Democratic White House candidate Barack Obama, told Ireland's TV3 channel that Palin was extreme and incompetent.

"I think she's a joke. I mean I always thought, she's a bad joke," he said. "But I always thought it was a colossal misjudgment of McCain's to appoint her as his running mate because she's not even borderline competent and what we know about her, or increasingly what we are beginning to know about her, is how very, very, very far to the right she is."

He said she did not believe in abortion "even in cases of incest and rape". Palin, who is governor of the US state of Alaska, was thrust into the spotlight in early September as McCain's surprise pick as running mate.

The 44-year-old mother-of-five has come under fire for her lack of experience amid concerns about her readiness to take over the presidency should something happen to McCain, 72.

Rushdie conceded there was one benefit to her arrival on the national political stage -- as fodder for US comedian Tina Fey, who bears an uncanny likeness to Palin and has mercilessly impersonated her on television.

"She has enabled Tina Fey to carry out some of the greatest political satire that anybody has carried out in America in my memory and everybody loves Tina Fey but now I think she's a national heroine," the writer said.