Average household energy bills will rise to £3,549 in October following the decision of energy regulator Ofgem to raise the price cap.
The record 80% hike will see a typical default tariff customer paying an extra £1,578. The rise follows a 54% increase in April, which saw average bills surge to £1,971 a year.
Ofgem Chief Executive, Jonathan Brearley, said:
'We know the massive impact this price cap increase will have on households across Britain and the difficult decisions consumers will now have to make. I talk to customers regularly and I know that today's news will be very worrying for many.
'The government support package is delivering help right now, but it's clear the new Prime Minister will need to act further to tackle the impact of the price rises that are coming in October and next year.
'We are working with ministers, consumer groups and industry on a set of options for the incoming Prime Minister that will require urgent action.'