Energy firm E.On will increase electricity prices by 7.7% and gas prices by 9.4% from January 18, the company has said.
The average dual fuel price will increase by 8.7%.
All of the major energy companies have now announced a price rise for UK customers.
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The Duke and Duchess of Cambridge met young people who have battled mental health issues on Saturday.
Former Chancellor Lord Geoffrey Howe was Margaret Thatcher's longest-serving Cabinet minister, also taking on the role of Foreign Secretary.
Lord Geoffrey Howe is known by many for his resignation speech which was seen as the catalyst which destroyed Margaret Thatcher.