Ofgem said British Gas, Britain's biggest energy supplier, had shown failings in its registrations, complaints handling and billing processes for business customers and over 6,000 new customers had experienced delays registering with the supplier.

The 9.5 million pounds comprises payments to affected customers and payments to a charity to help energy customers in need, Ofgem added.

British Gas said it voluntarily reported the issues to Ofgem after it introduced the new IT billing system.

"We invested in a new billing system so we could improve the service we provide to our business customers," British Gas said in a statement.

"At the time, this was a major undertaking - merging nearly 100 different systems into one. It didn’t go as smoothly as we would have liked so we reported this to Ofgem as a priority," it added.

British Gas said the issues have now been resolved and it has restored a "very good quality of customer service".

($1 = 0.8009 pounds)

(Reporting by Esha Vaish in Bengaluru; editing by Nina Chestney)