Washington: Apple Inc will refund consumers at least$32.5 million to settle a longstanding complaint that the technology company billed U.S. consumers for charges incurred by children through mobile apps without their parents' consent.

Under the terms of the settlement, announced on Wednesday by the U.S. Federal Trade Commission, Apple also will be required to change its billing practices to ensure it obtains consent from parents before charging for such in-app spending.

"Whether you're doing business in the mobile arena or the mall down the street, fundamental consumer protections apply," said FTC Chairwoman Edith Ramirez. "You cannot charge consumers for purchases they did not authorize."

She estimated that children spent millions of dollars without their parents' knowledge, with one mother telling the agency that her daughter spent$2,600 while playing the game "Tap Pet Hotel.