Millions 'paying over the odds'

Ofgem said that 4.3 million people without gas supply were being "short changed" by their suppliers, forking out on average £55 a year by not having access to the best dual-fuel deals.

It added that millions more who do not pay by direct debit - including six million pre-payment customers - are being penalised to the tune of around £1.4 billion a year.

Ofgem said in the initial findings of its seven-month probe into the energy market that it was looking at imposing a ban on unfair price differences.

But the report found that while some consumers were missing out on the full benefits of competition, the market was working well for most.

It said it found no evidence of an energy supply cartel and that consumers have benefited from the greater choice since the gas and electricity market was opened up to competition 10 years ago.

The study was launched earlier this year following a series of hefty price increases in gas and electricity.

There were concerns of price collusion after the big six suppliers hiked tariffs at the same time.

Ofgem confirmed it found nothing to back-up these fears or that suppliers were quick to raise prices and slow to cut them.

On the whole, consumers gave the market the thumbs-up, it said, but added that there needed to be a fairer deal for all customers.