MINISTERS should intervene and cap gas and electricity prices, union reps demanded yesterday as a new study shows that bills have soared by up to a third.

Before it ceased trading last November, GB Energy’s gas bills rose by 26 per cent, while its electricity bills rose by 32 per cent.

Electricity tariffs from Flow shot up by 18 per cent, while npower’s and SSE’s rose by 15 per cent, and E.ON bills by 14 per cent, according to figures gathered by general union GMB.

Among gas suppliers, LoCO2 has put prices up by 10 per cent, First Utility by 9 per cent and Bristol Energy by 6 per cent.

The union, which represents energy workers, claimed the figures show that energy companies are in “real trouble.”

GMB national secretary Justin Bowden said: “The pantomime that passes for UK energy policy and energy bills regulation continues.

“GMB has always ridiculed the very idea of a competitive market in a natural monopoly because it is a contradiction in terms that we all pay for through our energy bills.”

Mr Bowden branded energy regulator Ofgem a “purring pussycat,” saying its functions should be taken over by the government so ministers can directly cap energy bills.

Last week Theresa May said the energy market was “manifestly not working for all consumers” saying she would set out plans for reform “very soon.”

Her party was vocally critical of a Labour manifesto pledge to freeze energy prices at the last election.