Its comments came as M&S salads - which the retailer claims already meet Food Standards Agency (FSA) 2012 salt targets - were singled out for their high salt content in a survey from lobby group CASH (Consensus Action on Salt & Health).
According to CASH, which tested more than 270 salads and pasta bowls from supermarkets and chains such as KFC, Eat and Pret, M&S had seven out of 10 of the saltiest supermarket salads, including an avocado and feta salad (2.4g salt per 320g portion) and a Taste of Asia salad (2.83g per 258g portion).
Survey does not compare like with like
However, comparing salt levels in one salad weighing almost twice as much as another was not meaningful, M&S company nutritionist Claire Hughes told FoodManufacture.co.uk.
"I struggle with these surveys because they are not comparing like with like. Unfortunately CASH’s survey makes comparing salt levels in salads very confusing for consumers."
Moreover, if a salad were designed to be eaten as a main meal, then it might be reasonable for it to contain more salt than a side salad, she said.
"Internally we look at a range of factors when we are assessing salt levels, from salt per 100g, to salt as a percentage of GDAs and the meal occasion - is the product designed to be a main dish or a side dish for example?
"We also look at the range. For example, many of the salads in the Count on Us range would have a green traffic light label for salt."
94% of M&S products were already compliant with the FSA's stretching 2012 salt targets, claimed Hughes.
FSA salt targets - will DoH keep to 2012 targets?
The fact that the FSA's nutritional responsibilities are being transferred to the Department of Health has created uncertainty over the future of its salt, saturated fat and energy reduction programme, she acknowledged.
But this did not mean that the food industry was 'off the hook' or that the pressure to reformulate had eased, she said. "We started reducing salt well before the FSA started to campaign on the issue. It's something that we think is important for our customers and our business."
CASH: Industry could do better
CASH did acknowledge that some supermarkets had worked hard on reformulating salad recipes. “The average salt content in supermarket salads has been reduced by nearly a quarter (23%) from 1.64g/portion in 2005 to 1.26g/portion in 2010."
However, the industry still had far more work to do, argued CASHchairman Professor Graham MacGregor. “It is absurd that only six salads in our survey contained less salt than a packet of crisps."
CASH: Foodservice sector has more work to do
MacGregor, who recently accused manufacturers of overplaying the technical role that salt plays in processed foods in order to avoid the "nuisance and expense" of reformulation, accepted that supermarkets had made progress in recent years.
However, caterers had avoided a lot of the media flak, he claimed. "The FSA probably should have been much stricter with the catering sector."