Labour stands accused of hindering investment in energy and preventing suppliers from passing lower wholesale prices on though to consumer bills.
But Flint said the “astonishing admission” that two big six chief executives have said they will not reduce bills while the threat of a Labour price freeze exists should be a matter for the competition authority.
Earlier in the day energy minister Amber Rudd told delegates of the Energy UK annual conference that Labour should reconsider its proposal after energy bosses have claimed that reducing energy tariffs is more difficult ahead of a possible price freeze.
It “would ultimately drive up costs for the very consumers Labour say they are trying to help”, Rudd said.
Speaking to assembled press, Flint answered simply: “If they are keeping prices artificially high then report them to the CMA.”
One of the energy bosses who have claimed a price freeze promise may disadvantage customers is the chief executive of RWE-owned Npower, Paul Massara, who earlier this year said the company would not reduce retail prices as a result of the risk the price freeze poses.
At the same event, management consultant Poyry told delegates that it was aware of at least two potential new entrants to the UK energy sector which have stalled plans until the outcome of the next election.