Investors holding stock in the supermarkets sector seemed to get very twitchy this week ­ but perhaps with good reason. First, there was the news Tesco was knocking another £55m off its prices as the supermarket price war entered a new phase. And City nerves were further jangled by the non appearance of the Competition Commission's report. As parts of the report leaked into the national press and investors panicked, "there might have been a bit of stock dumping," said Nick Jones at Goldman Sachs. But he reckoned the "bellicose statements" from across the Atlantic at Wal-Mart's annual analysts' meeting "probably had something to do with it as well". "Wal-Mart sounded very aggressive, very positive about the international operations. And Tesco and co are still vulnerable to that." By the end of play Tuesday, Sainsbury's share price had slumped almost 4% to 358p, making it one of the worst performers in the FTSE100. Tesco's price cuts went down like a lead balloon with investors steadily abandoning the stock, bringing Tesco shares down 2% to 2383/4p. Safeway's shares fell 5p to end the day at 284p, Morrisons was down 41/2p at 165p and Iceland fell 41/2p to 3161/2p. The panic seemed to be largely over by Wednesday, although most stocks still slipped downwards. Tesco was the exception: its shares rose 21/2p to 2411/4p Investors must now wait for trade secretary Stephen Byers to reveal all. But there's nothing to be nervous about, said one analyst. "What few concrete proposals the commission has are largely unworkable anyway. " The supermarkets have probably got very little to worry about." If supermarket bosses are worried about their performance, at least they can console themselves with one fact: they are not running Marks and Spencer. There was no sign of investors rallying to M&S which saw its share price slip (albeit briefly) below the £2 mark for the first time in 10 years in the wake of profit downgrades from two influential analysts. {{NEWS }}