Ed Miliband today accused the Government of planning to make taxpayers pay the price of removing green levies from energy bills.
Downing Street did not rule out the possibility of paying for the levies with money raised from taxes or reductions in spending elsewhere, saying only that this would be the subject of discussions across Government ahead of an announcement by Chancellor George Osborne in his December 4 autumn statement,
Deputy Prime Minister Nick Clegg indicated that he was not willing to ditch measures like the Warm Homes Discount - which provides £135 a year to two million low-income families at a cost of £11 on average bills - but might be ready to shift the burden on to general taxation.
"What you'll be doing if you just scrap it, if you just roll it back overnight, is you'd be hitting the vulnerable hardest," Mr Clegg told LBC 97.3 radio.
"What I'm saying is, yes of course, this is what the Prime Minister and I will do in the coming weeks - look at all these policies to make sure that they're value for money.
"If we can bring them down but deliver the same objective, let's do that. We can also, for instance, look at simply paying that £135 to those two million lowest-incomes simply from Government revenue instead of from the bills. It has to be paid for in one way or another."
Mr Miliband said Mr Cameron's announcement, coupled with a planned annual review of competition in the energy market, was a "panicked" response to his pledge of a 20-month price freeze if Labour wins the 2015 general election. The Prime Minister has also come under pressure after his Conservative predecessor Sir John Major called for a windfall tax on the "Big Six" energy suppliers.
Speaking to small businesses in central London, Mr Miliband said: " Yesterday in weakness and panic, the Government made up a new policy on energy.
"Today, Nick Clegg has revealed their true intentions. To shift the burden from ordinary bill payers like you to ordinary taxpayers like you.
"Governments have always looked at this balance but this Government wants you to pick up the tab for its failure to stand up to the energy companies. That won't offer the real help that business and families need.
"They propose a panicked wheeze paid for by taxpayers. We offer a real freeze paid for by the big energy companies."
Mr Clegg rejected Labour's price freeze as a "con" which would "see prices go up, jobs go down, investment go down", but also attacked the "new theory emerging on the right of British politics which says it's all the fault of us caring about the environment".
The Liberal Democrat leader is reported to have only been told about Mr Cameron's decision to announce the plan at Prime Minister's Questions around 30 minutes before the Commons showdown with Mr Miliband, which was dominated by exchanges on energy policy.
The DPM refused to go into detail of how he heard about the move, but told BBC Radio 4's Today programme: "It wasn't something that I was fully expecting and it's not something that I fully agree with."
He did not accept that green levies were the main reason for price hikes, putting 60% of the increase down to rising wholesale costs in the energy market.
Setting out the next stages, Mr Clegg said he would talk with Mr Cameron to see whether the Government's objectives could be "delivered in a more cost-effective way".
He said: "We will stress test all these different levies. If we can deliver those objectives of keeping the lights on, insulating people's homes, helping the fuel poor, supporting our green economy for less - of course I don't want to see an extra penny on people's bills than is actually necessary - that is what we will do, as we always do in the coalition - whatever our differences, we resolve them."
But he added: "I'm not frankly entirely sure ... if removing all green levies which help two million people on very low incomes, which help support thousands of jobs in our green renewable energy sector - if that is what is meant I think that would be an own goal."
Speaking during a visit to online clothing company Asos's warehouse in Barnsley, South Yorkshire, Mr Cameron would not be drawn on whether he had ever taken his own advice and switched suppliers to find the best deal.
He said: "Switching energy suppliers can help people save up to £250, so that is a thing that people can look at but, as I said yesterday, we've also got to look at the taxes and charges and things that are added to people's bills to see if we can reduce the cost of those because I want not only help people pay their bills as we do but also help get those bills down.
"We want to do that sustainably for the future - that's what our aim is and we'll be making announcements at the Autumn Statement."
When asked if his own family had looked at their energy supplier to consider switching in the face of rising bills, Mr Miliband replied: "Yes we have, like any household.
"But the reality is that you can't just say to consumers 'it's your responsibility to fix a broken market'.
"It's the Government's responsibility to fix a broken market."