Woolworths shares have dived as much as 3.5 percent after the retailer said supermarket sales had slowed thanks to the phase out of single use plastic bags. As he posted a 12.5 percent better profit of $1.7 billion, chief executive Brad Banducci called for certainty amid the leadership speculation in Canberra. ABC's Peter Ryan says Mr Banducci warns the lack of certainty could harm consumer confidence.