TalkTalk will be Britain’s biggest residential broadband provider when it splits from the retail arm of Carphone Warehouse next year.
Harding, who previously held management positions at Thomas Cook and Woolworths, left Tesco in 2007 to head up Sainsbury’s convenience store division. She has also served on the board of property company British Land. Harding will leave Sainsbury’s next Spring.
Carphone’s retail division Best Buy Europe is headed by another former Tesco star, Scott Wheway, who spent 20 years at the supermarket.
Carphone’s chairman John Gildersleeve, also formerly a Tesco executive, is likely to have played a large role in the appointments.
Harding, a keen horsewoman, has been named in several surveys as one of the UK’s top businesswomen. Her racehorse Cool Dawn won the Cheltenham Gold Cup in 1998.
Last month, Carphone raised earnings guidance for 2009-10 on the back of strong first-half results.