The UK’s four biggest grocers have been accused of misleading shoppers with confusing and untrue claims that potentially leave them open to prosecution.

The BBC’s Panorama programme has uncovered a series of pricing tactics, some of which are in breach of consumer regulations, according to legal experts.

It has also commissioned a survey indicating that the public is losing faith in the claims made by grocers – with four in ten saying they no do not trust that their promotions, discounts and offers are genuine.

In the documentary, entitled The Truth About Supermarket Price Wars, Panorama reporter Sophie Raworth claimed she found mistakes and misleading claims at Tesco, Asda, Morrisons and Sainsbury’s.

After a trip to each of the big four grocers in a single day, Raworth found 17 items presented as a bigger pack for better value which were in fact worse value. Five were in Tesco, five in Sainsbury’s, four in Asda and three in Morrisons.

The programme uncovered a number of what it called misleading promotions.

Research into fabric conditioner on promotion at Morrisons, labelled ‘Now £2 - Offer ends Sunday’ had been £1.65 two weeks ago; Tesco £4 fresh chicken labelled as part of its Big Price Drop had been restored to its price of two months earlier which it had been sold at for the previous seven months; and products on the Asda website labelled as “Wow” deals were actually more expensive than they had been previously.

Tesco said its pricing practice had breached no rules. It defended the price rises before the Big Price Drop saying it was launched in a period of significantly higher food costs and said the campaign is intended to help combat inflation, not eliminate it.

Mintel retail analyst Richard Perks told Panorama: “If there was a price war going on at the moment we would have seen profits falling, or we would have severe warnings and that is just not happening. What we’re seeing at the moment is very much more about using your marketing budget as effectively as you possibly can.

“The name of the game is to be as clever as possible in how you promote and how you use your discounts and how you attract your customers… But it seems some customers are no longer convinced by these promotions.”

An Ipsos MORI survey of 1,546 shoppers carried out for Panorama reveals 42% of shoppers don’t trust supermarket offers and that the discounts are genuine; 31% said they were less likely to trust them now than in the past; while nearly half (47%) say they’ve felt misled by various offers.

Last December, the Office of Fair Trading warned supermarkets to stop using misleading pricing practices, or face “enforcement action”.

The Office of Fair Trading told Panorama: “We would be concerned about any misleading pricing or promotions and, with Trading Standards, we will look carefully at any findings Panorama shares with us.”