Supermarket chain Morrisons will come under more pressure on Monday amid expectations it fared badly over the Christmas trading period.
Its update for the six weeks to the end of December is likely to show like-for-like sales fell by more than 2% on a year ago, as the UK's fourth biggest grocer is squeezed by bigger rivals and discounters such as Aldi and Lidl.
The latest figure will fuel expectations that the chain's under-pressure chief executive Dalton Philips will be forced to downgrade the City's profit hopes.
Analysts believe Morrisons is struggling to compete because of its lack of grocery delivery service and limited number of convenience stores. Competition in the sector over the Christmas period has been as fierce as ever, with the big players focused on promotional deals and money-off coupons.
Tesco sharpened its performance after a disastrous 2011 and is likely to show a modest return to like-for-like sales growth later this week, while Sainsbury's will also be up by about 1% in sales figures on Wednesday.
The most recent set of figures from Morrisons in November showed like-for-like sales, excluding VAT and fuel, were down 2.1% after the Bradford-based firm admitted it had not done enough to advertise its promotions.
Despite a pledge to step up discounting and tactics to draw in hard-up shoppers - including a Christmas meal with all the trimmings from £2.49 per person - Morrisons is again seen reporting sales down by around 2%.
Broker Jefferies is even more pessimistic, believing same-store sales fell by as much as 2.8% as discounters such as Aldi and Lidl attract more business.
Mr Philips has led a major push to promote the chain's fresh food credentials, announcing an advertising deal with TV presenters Ant & Dec and sponsorship of hit shows Britain's Got Talent and Ant & Dec's Saturday Night Takeaway.
He is expected to signal a move into online shopping later this year, while the company hopes to have 70 convenience stores by the end of 2013.