LONDON (Reuters) - Debenhams , Britain's No. 2 department store group, posted record Christmas sales, helped by its breadth of products, appeal to a wide range of customers and online offer.

The group said on Tuesday sales at stores open over a year, rose 5.0 percent in the five weeks to January 5.

Debenhams said in the 18 weeks to January 5 period, a big chunk of the firm's fiscal first half, like-for-like sales rose 2.9 percent.

That compares to analysts' consensus forecast for the first half to end-February of an increase of 2 percent.

Online sales over the 18 weeks jumped 39 percent.

The firm said there was some increase in its promotional activity in the run-up to Christmas.

As a result, it now expects gross margin for the 2012-13 year to be 10 basis points higher than last year rather than 20 basis points previously guided.

Many store groups are finding the going tough as consumers fret over job security and a squeeze on incomes.

Debenhams has generally bucked the gloomy trend, also helped by its multiple routes to market and well received marketing campaign.

(Reporting by James Davey; editing by Kate Holton)