Coles shares fell as much as 12.8% to A$20.47, their worst intraday session and a more than five-month low, after the Australian supermarket chain said heightened competitor promotions had weakened early second-quarter sales. Cost-conscious shoppers compared prices across retailers and channels and used promotions and loyalty programmes more heavily. Supermarket sales growth slowed to 3.6% in the first four weeks of the second quarter, below Visible Alpha’s 5% consensus forecast, while Coles said first-half supermarket EBIT would be in line with the prior corresponding period and flagged higher fuel-related costs. The update reinforced concerns that Coles was losing ground to Woolworths, whose supermarket sales grew 6.1%.