Energy companies will be banned from charging "unjustified" prices under new proposals put forward by the watchdog Ofgem.

All energy suppliers are under scrutiny by the watchdog

The measures are aimed at securing a fairer deal for customers dealing with energy suppliers.

Ofgem launched a consultation on the proposals following a probe into unfair pricing at the end of last year.

No evidence was found of collusion by the "big six" but Ofgem blasted energy companies for failing to slash unfair prices quickly enough.

It wanted an end to premium prices for pre-paid systems and to see more than £500m slashed from bills.

Under the proposed new rules, suppliers would be obliged to provide an annual statement including a reminder of the customer's right to switch energy providers.

Written quotations would be given after doorstep sales, with proof for pre-payment customers that offers made were better than their current deal.

And there would be a new set of standards that all energy companies should meet to ensure they dealt fairly with customers.

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Customers could not be stopped from switching supplier without good reason.

The regulator's chief executive, Alistair Buchanan, said: ""This is an emphatic move by Ofgem to clear the decks of obstacles that prevent consumers from getting access to the best offers.

"All consumers will be given greater power in the market and small businesses in particular will have a stronger hand to play in the market."

If companies fail to agree on the proposals, the Competition Commission could be asked to intervene.