UK supermarket group Wm Morrison has beaten its rivals this year in terms of sales growth, but still faces challenges related to its takeover of rival chain Safeway, according to market research firm TNS.

According to the latest industry data, Morrisons’ sales rose 14% in the 12 weeks to 28 March compared to the year-ago period, reported Reuters.

The UK’s largest grocery retailer, Tesco, achieved sales growth of 11%, while second-placed Asda had sales growth of 10%.

Third-placed Sainsbury’s continued to struggle, achieving sales growth of only 1%, while its market share fell to 15.7% from 16.6% a year earlier. Tesco, Asda and Morrisons have all increased their market share.

TNS warned that Morrisons could have difficulties trying to turn around Safeway’s slumping sales. Safeway’s sales fell 3% over the period and its market share also fell.

“The Safeway business is a much larger entity than Morrisons, which will make the task that much more difficult. Morrisons is reputed for its ‘keep it simple’ culture, and it will be keen to maintain that ethos within the much larger scale business that it is now faced with,” Peter East, retail director of TNS Superpanel, was quoted by Reuters as saying.