To answer this, Lidl has stepped in to settle the debate by launching regular comparison shopping studies - putting its prices to the test against competitors SuperValu, Dunnes Stores and Tesco.

A store giant has abandoned a site for which it had obtained planning permission for a new store - allowing its arch rival to swoop. Developers were given the go-ahead for a new Lidl supermarket ...

And the winner is... Aldi. The German discounter beat its supermarket rival Lidl as the cheapest. The results showed a December shopping list of 56 groceries cost £100.29 on average at Aldi.

Today, Lidl launches a digital customer loyalty programme in Belgium and Luxembourg. Customers can now collect points in the Lidl Plus app, and then use them to get free products or discounts.