Energy secretary Ed Davey tells industry conference that latest round of price rises 'have not been fully and openly justified'

Ed Davey, the secretary of state for energy and climate change, has accused the big six energy companies of using customers as "cash cows" by raising bills unfairly.

But he also renewed his attack on Ed Miliband, describing the Labour leader's proposal to freeze energy prices as "intellectually bankrupt".

Davey was speaking at the annual conference of Energy UK, the lobby group for the power industry, on the day in which EDF became the latest firm to raise prices.

He noted the rise by the French group was more "modest" than others but urged consumers to vote with their feet by switching to cheaper suppliers. "Customers are not just cash cows to be squeezed in the pursuit of a higher return for shareholders," he said. "And frankly, the latest round of bill rises have not been fully and openly justified."

Davey said the energy industry faced a "Fred the Shred" moment where they could take action to be more responsible or risk being pilloried like the banks – specifically the former RBS boss Fred Goodwin.

But Davey was even more critical of Miliband, saying many of the problems that he was trying to sort out had been left on his plate by the former energy secretary. Davey said Miliband "should know better" than to play to newspaper headlines with "quick fixes" such as a price freeze.

Davey said he was absalutely clear that the role of government was not to fix prices. "This will have a huge detrimental impact on the investment we need to deliver secure energy supplies. And an investment squeeze would mean a huge black hole in Britain's energy security – risking blackouts and higher prices in the long run," he argued.

Davey admitted he was put under pressure by power companies to lift energy efficiency measures and other costs off bills. "Quite a few people have been trying to put pressure on the government," he said.