Tesco, Britain's biggest retailer, posted a fall in UK underlying sales in its first quarter.
The results showed its recovery plan following January's shock profit warning is taking time to gain traction.
The firm said today that sales at British stores open over a year, excluding fuel and VAT sales tax, fell 1.5% in the 13 weeks to May 26.
That compares with analyst forecasts of a fall of 1-2%, and a decline of 1.6% in the fourth quarter to February 25.
This included a fall of 2.3% over the Christmas trading period that prompted the retailer's first profit warning in over 20 years.
"Our performance in the UK has been steady during a challenging quarter for the industry as a whole," said the firm. "The industry remained very competitive through the quarter, with a significant amount of couponing activity," it added.
Tesco's first quarter misses the benefit to food sales of celebrations to mark the queen's diamond jubilee and the late spring bank holiday, which both fell in the company's second quarter.
The sales outcome also reflected a tough comparative, as last year a royal wedding and the spring bank holiday fell in the first quarter.
Tesco, the world's third largest retailer with over 6,000 stores in 14 countries, said first quarter sales for the group rose 2.2%, including petrol.
The company's European like-for-like sales increased by 0.4%, with Ireland delivering its first full quarter of postive like-for-like sales growth since 2010. It also saw improved performances in Poland and Slovakia.
But it noted that continued uncertainty over the future of the euro zone and the potential impact of any further disruption has resulted in very low consumer confidence, particularly in Central Europe.
"At this early stage of the year, we are performing in line with market expectations for the group. The outlook for the year as a whole remains unchanged," it added.
In April, chief executive Phil Clarke, a Tesco career lifer who as a youth stacked shelves in his local store, slashed expansion plans for the retailer's main British chain and said he would spend over £1 billion on improving stores and online shopping in a bid to reverse the decline in market share.
He said the UK business needed more staff, smarter stores, lower prices and better products after becoming too focused on cutting costs and boosting profit margins. But he did not give a timetable for the plan to deliver better sales.
