Darlene Egelhoff told Us Weekly she thinks Montag was under the influence when she wed Pratt last month in Mexico. She also predicted "The Hills" stars' marriage would expire within six months.
"I am sure she is just hurt and reacting crazy because she wasn't there," Usmagazine.com quoted Pratt as saying Thursday on Ryan Seacrest's KIIS-FM radio show. "I can't wait to prove her wrong and be married for the rest of our lives."
He also said he and his new bride probably won't be spending the holidays at the Montag family home this year.
"After that statement (to Us Weekly,) the Pratts, as in Heidi and Spencer Pratt, will have their own Christmas tree out here," he told Seacrest.