The claims, in a newspaper yesterday, stated E.ON has paid out £6 million a year to Age UK in return for the charity pushing expensive tariffs to the elderly.
E.ON has confirmed they had a “commercial relationship” but the supplier said its tariffs were competitively priced and Age UK has rejected any allegations of wrongdoing.
The Commission said: “The Commission is aware of concerns raised in the media regarding Age UK’s partnership activities with E.ON.
“The Commission is in contact with both Age UK and Ofgem to determine what regulatory role the Commission might have and any action that might be necessary.”
Shadow energy secretary Lisa Nandy called on the Commission to investigate. She said: “The Charity Commission should investigate whether Age UK has broken the rules because it’s vital the public can have confidence in the good work charities do.
“It’s more important still that ministers fix our energy market to make it more transparent and stop backroom deals, wherever they occur.”
Ofgem also said it was “examining the claims”, adding: “Ofgem has a track record of punishing firms who mislead consumers and we will look at carefully at these claims.”
Energy Secretary Amber Rudd said she was taking the allegations “very seriously” and had asked Ofgem to investigate further.
An English tabloid said it found details of E.ON payments in Age UK’s annual accounts.
It is claimed the charity had been recommending a special E.ON tariff in leaflets and booklets, stating it was “great value” and “helps save energy and money”.
Age UK has been paid at least £6m every year, receiving around £41 for every person that signed up, it was reported.
It is claimed that the tariff, on average, costs pensioners £245 more than they would pay on E.ON’s cheapest deal.
A spokeswoman for E.ON said: “Our current Age UK tariff was the cheapest product of its type in the UK when it was launched in January. Customers can switch between products at any time without incurring any costs.
“If a customer is on a fixed tariff and they opt in for a price alert, and if we issue a new tariff that is cheaper, we will automatically notify them of that.
“But in line with Ofgem’s rules we can’t switch people without their consent.”
In January Age UK criticised the big six energy firms for overcharging and warned more than 4.1 million older people were “anxious” about high heating costs.