The power company Powergen is putting up its gas prices by 24.4% and electricity prices by 18.4%.
The price increases, from 10 March, will affect about six million customers in the UK.
Powergen is the latest power supplier to announce big price increases in response to the rising wholesale price of gas.
It says the wholesale price of gas has now risen by 70% since January last year.
The company says the increases will add Ј107 to its average annual gas bill and Ј56 to its average annual electricity bill.
A company spokesman, Nick Horler, said: "We shielded our customers from the impact of these costs for as long as possible."
Powergen is owned by the German power company E.ON.
Its decision follows similar increases from British Gas, EDF Energy, Scottish Power and Npower.
The company last put up its domestic gas prices last September when they rose by 12% alongside a 7% rise for electricity customers.
Today's rise means that since January 2004 Powergen has imposed five price increases on its gas customers and four on its electricity customers.
(BBC)
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