Nov. 4 (Bloomberg) -- Marks and Spencer Group Plc will extend the sale of branded groceries across Britain, seeking to retain shoppers reluctant to buy only the retailer’s own food labels, after a regional trial was successful.

Up to about 400 branded goods including Unilever’s Marmite spread, Fairy dishwashing detergent and Pantene shampoo will be added to all outlets over the next year, the London-based retailer said. The trial, announced in May of last year, took place in 54 stores in northeast and southeast England.

Marks, which is also the U.K.’s largest clothing retailer, reports first-half earnings at 7 a.m. today. Known for premium foods like shortbread biscuits and prepared meals, M&S said none of its products will be removed, with the rival brands limited to categories where the retailer has a low market share or doesn’t make an equivalent product.

“It will be so much more convenient for our customers to get what they need from M&S rather than having to go elsewhere,” Executive Chairman Stuart Rose said in the company’s e-mailed statement today.

Private labels are more profitable for retailers than other companies’ goods, and M&S broke with its own tradition last year when it announced the trial. Marks’ food range is typically more expensive than its largest grocery rival, Tesco Plc.

“I think it will be marginally positive,” Simon Kelley, an analyst at ICAP Securities who rates M&S “sell,” said by phone. “It’s an attempt for customers to do their one-stop shop at M&S, and we know there are certain brands that it can’t compete with, so it will complement their range. I’d prefer if they expanded their existing private-label offer.”

Each M&S store will have between 50 to around 400 branded goods, according to its size.

The median estimate of 12 analysts surveyed by Bloomberg is for first-half pretax profit to decline by 4 percent to 285.6 million pounds ($468.6 million).

To contact the reporter on this story: Sarah Shannon in London at sshannon4@bloomberg.net.

Last Updated: November 3, 2009 19:00 EST