Tesco is investigating a computer hacking attack that is reported to have exposed the login names and passwords of more than 2,000 customers.

Hackers uncovered the usernames and passwords of website users and posted them on a popular text-sharing site. Some customers are believed to have also had Clubcard vouchers stolen.

“We take the security of our customers’ data extremely seriously and are urgently investigating these claims,” said a Tesco spokesman. “We have contacted all customers who may have been affected and are committed to ensuring that none of them miss out as a result of this. We will issue replacement vouchers to the very small number who are affected.”’

It is not the first time Tesco has been targeted. In early 2013 a number of Clubcard holders had vouchers stolen by cyber criminals.

Last month the BRC reported a rising tide of cyber crime, with hacking attacks identified as the  biggest threats to businesses.