The traffic light labelling favoured by the Food Standards Agency appears to be foundering after just five months, with 18 manufacturers and retailers opting for the rival GDA scheme compared with just four backing the FSA.

The latest figures reveal the size of the split in the industry with not one ­manufacturer opting for the traffic light approach. Retailers, however, are divided as Tesco, Somerfield and Morrisons have chosen GDAs, while Sainsbury's, Waitrose, Asda and The Co-operative Group have gone for traffic lights.

However, in Tony Blair's speech on promoting healthy living this week, he warned that if the industry did not come together then government would act. "We are encouraging the industry to adopt the FSA's clear system for labelling. We are prepared to act if the voluntary system does not work."

A spokeswoman for the FSA said it was still pleased that manufacturers were recognising the importance of front-of-pack labelling. "However our research is clear: the use of traffic light colour coding is key to helping people use front-of-pack labelling schemes quickly and easily. It is encouraging that since we recommended our approach, more than a third of the retail market has signed up to schemes that meet our principles."

Spar group trading director Peter Miller said the convenience group was currently considering its options.

Marks and Spencer and Lidl also said they would be making a decision in the near future.