WASHINGTON -- Paris Hilton's mother doesn't share John McCain's sense of humor.

McCain, the Republican presidential candidate, said last week that his campaign ad mocking Democrat Barack Obama with images of Hilton and singer Britney Spears was part of an attempt to inject humor into the presidential race.

On Sunday, Hilton's mother, Kathy Hilton, a McCain donor, registered her disapproval.

"It is a complete waste of the country's time and attention at the very moment when millions of people are losing their homes and their jobs," Kathy Hilton said in a short article posted on the liberal Huffington Post Web site. "And it is a completely frivolous way to choose the next president of the United States."

The ad plays on Obama's popularity by dismissing him as a mere celebrity, like Hilton and Spears. The Obama campaign has said the ad is proof that McCain would rather launch negative attacks than debate important issues.

McCain on Friday denied that his campaign had taken a negative turn, saying, "We think it's got a lot of humor in it, we're having fun and enjoying it."

Kathy Hilton, however, was unpersuaded, calling the ad "a complete waste of the money John McCain's contributors have donated to his campaign."

Kathy Hilton and her husband donated a total of $4,600 to McCain's campaign earlier this year.