Tesco is extending its Scan as you Shop service to a further 20 stores, in a move it said would help thousands of customers save time at the checkout.

The extension of the service, which allows customers to scan products as they walk through the store, as well as keep a tally of their spending, means it is now available in almost 350 stores across the UK.

Tesco has also launched a new TV ad to publicise the service.

“We want to make it as easy as possible for customers to shop with us,” said a spokeswoman. “Scan as you Shop is already used by over 600,000 customers every week, and not only saves time at the checkout, it enables customers to track their spend as they go, too. This new trial will mean more customers than ever before can benefit from the service and check out in a matter of seconds.”