Asda CEO Andy Clarke has said the UK retailer will "leave no stone unturned" in rebuilding consumer confidence "dented" amid the horsemeat contamination scandal.

Clarke said Asda, which last week recalled a chilled sauce line after it tested positive for horse DNA, would adopt a "belt and braces" approach to further testing.

"We've checked everything the Food Standards Agency has asked us to check but we're not stopping there. We're going to be testing products so that we can reinforce with confidence that those processed products are what it says on the label," Clarke told reporters yesterday (21 February).

Clarke said he was "shocked" when news of the contamination first emerged last month after frozen beef burgers on sale at retailers including Tesco and Aldi were found to contain horse DNA.

The Asda CEO emphasised the cautionary approach the retailer had taken to the contamination by underlining the fact it had pulled burgers from its shelves because they were made at the same plant that had produced the lines that contained horse DNA - even though the company's tests on its products were negative.

However, Clarke said that, as chief executive, he took responsibility for the contamination of Asda's Chosen By You Beef Bolognese Sauce with horse DNA. "At the end of the day, our customers come into our stores and expect to buy what it says on the label. In one case so far, that's not been the case. I feel very responsible for that. I'm the chief executive of the business," he said. "I'm leaving no stone unturned of addressing the issue in our own network. It may have happened up the supply chain; to be frank, that's not our customers' problem. We're working very clearly with our suppliers to identify where the issue come from and we'll get to the bottom of it."

Nevertheless, when Clarke was asked whether retailers should take broader responsbility for the contamination due to the economic pressure that could be on suppliers down the chain, he said: "We're asking ourselves all the questions [but] there's no excuse for something criminal happening anywhere in the network. That's just fundamentally wrong."

Asda said there had been signs consumers were changing what they buy in reaction to the contamination scandal. "This is not a food safety issue. The consumer has taken that to heart. There has been some sales impact across some categories," Clarke said. "What's interesting is that consumers are switching. Veggie meals, meat-free products have taken a lift."