CONCORD, N.H. -- Heidi Quigley says she was a volunteer for Republican presidential candidate George W. Bush until his campaign recruited her for a negative ad.

On Monday, Bush and his chief rival, Arizona Sen. John McCain, promised to refrain from running negative television ads.

But Quigley said Tuesday that the Bush campaign asked her this past weekend to appear in a television commercial and make negative comments about McCain.

Quigley said the interviewer asked her to compare Bush's tax plan to McCain's. When she said she didn't know enough to feel comfortable commenting, the interviewer told her to say that Bush's plan would leave more money in the hands of taxpayers, while McCain's would send more money to Washington.

"When I look at it, (Bush) is saying (Steve) Forbes is doing a negative commercial, but so is he by feeding me negative things about McCain," Quigley said. "I didn't feel right."

Quigley is now working for McCain.

Bush, who was campaigning in South Carolina on Wednesday, said Quigley should not have been asked to criticize McCain.

"The ad will not run," Bush said. "I'm going to treat my friend and opponent with respect. He deserves to be treated with respect. He's a buddy, but he's not right on the tax plan."

The dispute illustrates how heated the contest between Bush and McCain has become in the state that will host the first presidential primary Feb. 1. Bush is the clear front-runner among Republicans nationally, but McCain is ahead in several recent New Hampshire polls.

Quigley, a senior at American International College in Springfield, Mass., said she started volunteering for Bush in Manchester last month. Last weekend, the campaign asked her and several other volunteers to film interviews, she said.

The ad was shot around the corner from Bush's campaign headquarters in Manchester, she said. She was asked to say her name and her hometown, and was instructed to look at the media consultant asking questions off-camera, rather than into the camera, she said.

McCain's campaign said the technique was misleading because it would give the impression that random voters were being interviewed in "man on the street" style.

"What they've done with this girl is deceitful," said Mike Dennehy, McCain's New England political director.

But Bush's campaign defended the filming as common practice: campaign supporters using their own words to comment on the candidate's proposals.

Supporters of the Texas governor also said McCain's campaign should not judge the commercial unless and until it airs.

"How do you know it was a `man on the street?"' said Bush's state campaign director, Joel Maiola. "Until it's run, there's not a lot there."

Rush Schriefer, of Maverick Media of Austin, Texas, who conducted the interviews for the Bush campaign, denied feeding anyone their lines.

"We would explain Governor Bush's position on an issue and ask them to comment on it. If someone said they felt uncomfortable with what we were talking about, certainly they were under no obligation to talk."