She was also criticised by one senior industry figure who suggested Government intervention would drive some companies out of the market and make it even less competitive.

The Government has faced repeated calls for a fixed price cap on energy tariffs amid accusations that the so-called Big Six energy companies are not competitive enough on pricing.

Downing Street has refused to be drawn on what the policy might be, but would not rule out imposing a cap on tariffs

One suggestion being considered is that energy companies could be forced to accept a “relative price cap” which would peg their most expensive tariffs at no more than 6 per cent above their cheapest rates.

Although Mrs May has threatened to intervene several times in the past, it is the first time she has made a concrete commitment to taking action. One Whitehall source said she could set out her plans as early as next week.