Stronger action is needed to ensure energy customers get a fair deal, a committee of MPs has told the regulator Ofgem.
The MPs have called on it to be less timid in dealing with "anti-competitive" behaviour by suppliers.
They also warned that recent plans by Ofgem and the government might still fail to help customers make meaningful price comparisons "at a glance".
Ofgem said it would analyse the details of the report before responding.
The report of the Energy and Climate Change Committee said: "We find it unsatisfactory that Ofgem should be so hesitant about launching preliminary investigations into potentially anti-competitive behaviour.
"We understand that Ofgem plans to reduce barriers to competition... but we believe that a more proactive approach should be adopted."