From 1st October, around six million UK households are expected to be in fuel poverty, according to figures from National Energy Action.
This marks an increase from 5.6 million households currently affected.
The new price cap announced by Ofgem will result in a typical annual energy bill of £1,717, which is 9% higher than the current rate.
This rise comes as many pensioners miss out on the Winter Fuel Payment, including those who do not qualify for means-tested benefits or who are eligible for pension credit but do not receive it.
Energy bills had decreased slightly over the summer, but the upcoming increase will coincide with the colder months when energy usage typically rises.
Energy debt has also reached record levels, with customers owing over £3 billion.
National Energy Action highlights the need for all eligible households to be enrolled in means-tested benefits to access energy bill support.
National Energy Action Chief Executive Adam Scorer said: “Struggling households are in the third year of an energy crisis. Even before the crisis, our clients had no slack in their budgets. Three years on, they are mired in record levels of energy debt and severely rationing their energy.
“There is still time for Ofgem and UK government to act for those at greatest risk, but without support, this winter.
“Actively reduce their levels of debt and extend support beyond the hard edge of means-tested benefits.
“Government says it can only stretch the financial elastic so far, but they are cutting off support from those who have zero flexibility in their own budget, with no choice other than debt or going cold.”
