Warning supermarket loyalty 'challenges' could cause overspending

3 hours agoJennifer Meierhans,Business reporterGetty ImagesNew supermarket "challenges" that reward shoppers with extra loyalty points for buying more could lead to overspending, consumer groups have warned.Four of the UK's biggest supermarkets - Tesco, Sainsbury’s, Asda and Morrisons - are now offering members of their loyalty schemes bonus points if they hit spending targets.The supermarkets all say their…