Sainsbury's shares have plunged despite rising sales as the company admitted trading conditions are bleak. The supermarket beat market expectations to post like-for-like sales growth of 4.3 per cent for the 16 weeks to October 4. But stock fell 10 per cent in an already beleaguered market on the back of the announcement. The market took chief executive Justin King's comments that the economic environment was "particularly challenging" as a sign that it is downhill from here for the supermarket. Panmure Gordon stockbrokers said: "We think that this is as good as it gets and see margin pressure evolving over the next 12 months."