Apple will refund consumers at least $32.5 million (£19.87 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 (January 15) 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.

"A basic principle of consumer protection is that a company must obtain consumers' informed consent before charging them for any goods or services. Today, we're announcing that Apple has agreed to settle a Federal Trade Commission complaint alleging that Apple fell short on that principle," said FTC Chairwoman Edith Ramirez.

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.

Ramirez said the commission had received "tens of thousands of complaints" from consumers over the unauthorized purchases through apps such as Dragon Story and Tiny Zoo Friends.

In a memo to employees, Apple CEO Tim Cook referred to a class action settlement reached in June which required the company to pay around $100 million to parents whose children made unauthorized purchases.

"It doesn't feel right for the FTC to sue over a case that had already been settled. To us, it smacked of double jeopardy," Cook wrote. "However, the consent decree the FTC proposed does not require us to do anything we weren't already going to do, so we decided to accept it rather than take on a long and distracting legal fight."

The FTC complaint alleges that Apple does not inform account holders that entering their password in the company's App Store opens a 15-minute window in which children can incur unlimited charges with no further action from the account holder

While the refunds will be available for purchases through apps aimed at children, all Apple apps will get new disclosures, the wording of which has not yet been finalised.

Presented by Adam Justice