Green tariffs will count as one of four core tariffs energy suppliers are allowed to offer under Ofgem's Retail Market Reform (RMR), the regulator said today.

Announcing its “countdown to a simpler, clearer and fairer energy market”, Ofgem clarified there would be no exceptions for renewables tariffs.

A cap on the number of tariffs energy companies can offer will go live later this year, along with a ban on “dead” tariffs.

Prime minister David Cameron lent his weight to the proposals, reiterating a pledge to use the Energy Bill to make sure the reforms go through.

He said: “I made a personal commitment to help get energy bills down – and I’m delighted that Ofgem are taking that forward. The package announced today is a huge step towards energy bills that are more fair for everyone. This is about putting people before profits.”

Ofgem chief executive Alistair Buchanan urged energy companies not to wait for the legal process to reform their tariffs.

He said: “We are now counting down to the most radical shake-up of the energy retail market since competition began. We know suppliers are serious about wanting to restore consumer trust and they need to grasp this golden opportunity to change their behaviour.”

Industry body Energy UK said suppliers have already “dramatically reduced” the number of tariffs. Chief executive Angela Knight said: “The concerns of customers and politicians have been heard loud and clear by the companies. Clear choices are here to stay, and switching is faster and easier than ever before. A look at suppliers’ websites shows how much work has already been done.”

Consumer groups welcomed the announcement, but warned more work was needed to earn customer trust. Mike O’Connor, chief executive of Consumer Focus, said: “Mere compliance with the reforms is not a sufficient goal. If these reforms are going to earn consumer trust we will need to see a real transformation in the behaviour of energy companies and in the culture of the market.”

A consultation on the final RMR proposals, including the wording of proposed licence conditions, will be published around the end of March.