Energy regulator Ofgem has decided not to lower the standing charge.
The standing charge is paid by energy customers regardless of how much energy they use.
This means that people in South Wales will continue to pay £350 a year.
National Energy Action’s director of policy and advocacy, Peter Smith, said: “There is significant public concern around how high standing charges are.
“Tens of thousands of individuals and organisations responded to Ofgem’s consultation in support of reform.
“All major political parties made promises in their manifestos to reduce standing charges.
“The lack of any significant reform is therefore extremely disappointing.
“Households that use prepayment meters are particularly impacted by the continuation of high standing charges.
“When their credit has been used up, standing charges accrue as a debt on the meter that must be cleared in full before accessing energy again.
“We know that the higher standing charges are, the longer households are needlessly left without being able to use energy.”