The full extent of the problems facing the U.K.'s "big four" supermarket chains was underlined on Thursday, with a profit warning by WM Morrison sending shares in the sector sharply lower.
The country's fourth biggest grocer, WM Morrison, which holds 11 percent of market share, saw its shares plunge around 8 percent after posting its lowest profit in five years. It also slashed its forecast for 2014.
(Read more: UK grocer Morrisons slashes profit expectations)
Analysts heaped criticism on WM Morrison, saying its strategy had become muddled -- it both hopes to return to its heritage as a "value retailer," but is also trudging on with expensive online and convenience projects.
This may be indicative of an underlying trend that analysts said other chains also faced, that of a lack of direction in the middle-ground between budget and high-end retailers.
In decades gone by, Tesco and its peers rose to prominence with only themselves as competition. This landscape has radically changed, however, with new entrants at both the higher- and lower-end.
Waitrose, an employee-owned retailer, rose out of near-obscurity in the early 2000s and now continues to post record earnings with its top-of-the-range offerings and "upmarket" reputation. Meanwhile, at the lower-end, German retailers Aldi and Lidl have eaten away at the big-four's market share, because of their success at targeting budget conscious customers.
(Read more: Sainsbury's Justin King steps down, shares drop)