She's no Ashlee. Hilary Duff slams reports that she had been caught lip-synching during a concert in Mexico last weekend. The former Disney star's camp blames the incident on a technical setback.

"She was not lip-synching. It was faulty equipment. There was no sound coming out, but she was singing," her rep denies.

The 20-year-old Lizzie McGuire's rep explains that Duff relied on local sound equipment during the Saturday show rather than her own. The microphone was accidentally set on mute for the first few seconds of the singer's performance and then was fixed causing her to look like she was lip-synching. The rep insists she does her own singing.

Footage of the incident has made its round on the Internet where Duff is caught leaning over the microphone apparently singing but her voice can't be heard.

Duff is on her "Dignity" tour and is scheduled to continue in Mexico this week with three more stops before moving to Brazil and Australia.