The government has rubbished claims by a senior opposition politician that it has changed its policy on front-of-pack nutrition labelling.

Last week Asda announced it had decided to introduce a hybrid approach combining multiple traffic lights and Guideline Daily Amounts and quoted new health minister Dawn Primarolo as supporting the initiative.

"We welcome this move by Asda. It's great news for consumers who can find nutrition labelling on food confusing," she said. "We know from research that the traffic-light colour code is quick and easy for people to use when they shop. We hope that many more retailers adopt the labelling in the future."

Despite the apparent endorsement of traffic lights, Primarolo's comments were seized on by shadow health minister Stephen O'Brien as evidence the government no longer supported multiple traffic lights alone as the best approach to signpost labelling and had switched to supporting a hybrid approach.

"It is good to see that another major food retailer has judged the Food Standards Agency's traffic-light labelling inadequate for properly informing consumers of the nutritional value of their diet," he said.

"We welcome the government's complete change of policy of food labelling in now supporting what we have been advocating all along. It is just a shame Primarolo hasn't announced it to MPs first."

But a spokeswoman for the Department of Health said it was "not the case" that the government had made a u-turn over its support for the FSA's pure multiple traffic lights approach.

"There's no policy change and the government is still very much in favour of the policy set out previously," she said. "All Dawn did was to welcome an initiative that will give people choices."

Asda's move has also been praised by the FSA itself. In the agency's press release, chair Dame Deirdre Hutton said: "It's encouraging to see that Asda's consumer research backs up our own - showing that traffic-light labels are what shoppers overwhelming want and need, to help them make healthier choices at a glance."