"We experienced an unforeseen technical fault which resulted in the forced cancellation of many orders due to a complete system failure," Tesco said on Twitter after customers complained via social media about cancellations and delays.

The supermarket chain said it was working to resolve the issue and it was confident the problem would be fixed soon.

Tesco said in a tweet it could not download customer order details, after numerous customers took to Twitter to complain about cancellations.

Customers would be not be charged for cancelled orders and would be offered a 10 pound e-voucher as compensation, Tesco said in a text message sent to affected customers.

"Currently experiencing an IT issue which is affecting some grocery home shopping orders," the company said in an emailed statement to Reuters.

Last year, 2.5 million pounds was stolen from some 9,000 customers of the retailer's banking division.

(Reporting by Sanjeeban Sarkar, Rahul B and Noor Zainab Hussain in Bengaluru; editing by David Clarke)