Cornish denies affair with Ryan Phillippe

Abbie Cornish

Australian actor Abbie Cornish has dismissed reports she is to blame for the breakup of Reese Witherspoon and Ryan Phillippe.

The 24-year-old from NSW has been accused of having an affair with Phillippe on the Texas set of their new movie, Stop Loss.

A witness allegedly spotted Phillippe and a woman who appeared "to fit Cornish's description" kissing at a sushi restaurant.

"It's not true," Cornish's representative told America's Us magazine.

"They are co-stars and that is it."

Other reports allege Witherspoon ended her marriage after she discovered romantic messages Phillippe had written to Cornish on his mobile phone.