Tesco, M&S and Morrisons see sales slide over Christmas
Like-for-like sales at Morrisons have fallen 5.6%, in the six weeks to 5 January, sending shares tumbling by 7%.
It said a lack of online presence and competition by cut-price shops, such as Lidl and Aldi, were behind the fall.
Tesco's like-for-like sales also fell, down by 2.4% during the Christmas period, and its shares fell by 4%.
The supermarket giant said the fall was partly due to a "weaker grocery market" in the UK.
Robert Peston reports.
09 Jan 2014