By Saskia Koopman Sainsbury’s chief executive Simon Roberts has cautioned that new government measures will hit shoppers with higher prices by adding £140m to the supermarket’s costs. These include a National Insurance hike, and a rise in the UK minimum wage. The increased National Insurance contributions, as announced by Chancellor Rachel Reeves in her Autumn Budget, will surge from 13.8 per cent, to 15 per cent, on earnings above £175. “The impact on National Insurance was unexpected and is coming fast”, Roberts said. “It will have a very significant impact on our cost base… and our supplier…