Dixons Carphone has admitted that details belonging to almost 16 million of its customers were exposed in two data breaches last year.

The electronics retailer, which owns Currys PC World and Carphone Warehouse, said around 10 million records containing personal data may have been accessed in 2017, up from an initial estimate of 1.2m people.

It said the data was non-financial information such as names and addresses and there was no evidence any of the records had been used for fraud. But it will write to affected customers after finding signs that some of the data had left its systems.

Separately Dixons Carphone has been investigating “an attempt to compromise” 5.9m credit cards, bringing the total number of records affected to 15.9m.

It said the credit cards were mostly protected by chip and pin.

Alex Baldock, chief executive, said: “Again, we're disappointed in having fallen short here, and very sorry for any distress we've caused our customers. I want to assure them that we remain fully committed to making their personal data safe with us."