Tesco has been forced to make a major change on how it displays its deals following complaints it could be breaking the law.

The supermarket was accused of potentially "breaking the law" after failing to present unit pricing – such as the price per 100g – on products with Clubcard promotion prices.

Consumer group Which? has reported Tesco to the UK competition watchdog, the Competition and Markets Authority (CMA).

The supermarket giant previously said its Clubcard prices promotions were reviewed by Trading Standards which "formally endorsed" its price labelling.

It added that it was "disappointed" by the "ill-founded claims" by Which?

Shoppers can use unit prices to compare the best value for products.

This week, Tesco’s UK chief executive Jason Tarry wrote in a blog: "If you are in store, you will now start to see that the way that we display our Clubcard Prices will not only show the total price, but also the unit price of the product (by volume or weight), to allow a direct comparison of the price per unit between the Clubcard Prices offer and the price of alternative products.

"This is something that we have been planning to do for some time, and I am really pleased that we are ready to make the change.

"Over the coming weeks, these changes will appear in all our stores, as our colleagues update millions of price labels on the shelf edge. We will also be adding these unit prices to our Clubcard Prices deals online."