Five water firms will be provisionally allowed to hike their bills by more than previously granted - raising an extra £556million in revenue, the competition watchdog has said.Anglian Water, Northumbrian Water, South East Water, Southern Water and Wessex Water all argued in March that an original decision by regulator Ofwat last December had left them unable to meet the regulatory requirements set out for them.Independent experts appointed by the Competition and Markets Authority (CMA) said Anglian and Northumbrian should be allowed to increase their bills by a further 1 per cent, Southern by 3 per cent, South East by 4 per cent and Wessex by 5 per cent.But David Henderson, chief executive of Water UK which represents water firms, came under fire on BBC Radio 4's Today programme over why shareholders cannot 'take the hit' for extra investment in infrastructure - rather than consumers.It also comes after water firms have paid out more than £112million in bonuses and incentives over the past decade - despite ongoing issues over sewage and pollution.Southern Water had already been allowed a 53 per cent rise to average bills over the next five years in the December ruling but had appealed for another 15 per cent.Anglian Water had been allowed 29 per cent and asked for 10 per cent more, while South East Water had been granted 24 per cent and asked for a further 18 per cent.Wessex and Northumbrian Water - who were both allowed a 21 per cent increase originally - asked for another 8 per cent and 6 per cent respectively.The CMA said a provisional decision allowed for 21 per cent, or an additional £556million in revenue, of the total £2.7billion the five firms requested.