The sales slump at Somerfield stores acquired by The Co-operative Group is worse than previously thought.

In the summer, like-for-like sales in stores yet to be converted to The Co-operative fascia were understood to be around 2% down year on year a marked improvement on the 12.2% slump reported earlier this year.

However, speaking to The Grocer at the IGD Convention, MD of food ­retail Tim Hurrell admitted "it is worse than that".

"It's not surprising ­because you've got the Somerfield fascia and The Co-operative's own brands so there are a lot of mixed messages," he said. "You've got under-investment because we haven't invested the money in them yet. It takes time for customers to come back."

The fall was not as bad as the slump experienced by Safeway stores after their acquisition by Morrisons, he insisted, claiming that he remained upbeat.

The stores that had been converted were now ­trading 5% above the Somerfield stores, he said, adding that the business as a whole was in "great shape" and profits would be "significantly up" on last year. "Sales are tough but not unexpected," he added. "The future is bright."

In January, the Co-op will launch a new ad campaign, including TV, online and leaflets, as the retailer looks to drive up its 7.5% market share. "We are spending a lot of money," said Hurrell. "This will be a whole new approach."