All four parties said they were committed to more renewable energy
By Victoria King
Political reporter, BBC News
Climate change - some have said it's the elephant in the election room. The thing that every party claims to really care about, but none seems to want to talk about.
Maybe so, but for 90 minutes on Monday, Labour, Conservative, Lib Dem and Green representatives went head-to-head on the issue in front of bodies such as Greenpeace, Oxfam, Christian Aid and the WWF.
Climate Change Secretary Ed Miliband was the most combative; as the only one with any concrete actions - or lack of actions - to defend, he chose to go on the offensive.
His Conservative shadow Greg Clark talked most about consensus. It was the broad agreement between parties that made it an unsatisfying election battleground, he said.
For the Lib Dems, Simon Hughes set his party up as the most ambitious of the main three on green matters. As Mr Miliband put it: "Simon says, 'My plan is bigger than your plan'."
There was conflict between Mr Hughes and Darren Johnson of the Greens, possibly because they share many of the same potential voters.
Mr Johnson said his party was prepared to be green and unpopular - a necessary combination, he said, if you are going to make the right decisions on climate change.
'Ed's a nice guy'
The Ask the Climate Question hustings was chaired by the environment editor of the Independent, Michael McCarthy, with questions ranging from nuclear power to emissions reductions.
Mr Miliband repeatedly came under fire over Labour's record. The general consensus from the other parties was that he personally had made considerable effort since taking office, but it was too little too late. Oh, and everyone thought he was a decent bloke.
"Our critique of the government is not [of] Ed's intentions," said Mr Clark, but why has a government "capable of making a difference" failed to do so? Why are we worst in Europe on renewables? he asked.
"Ed, nice guy that he is, has got a job at risk because we want to take that job from him," said Mr Hughes.
"We have to confront Ed on the fact that he talks a good talk, but targets aren't met.
"It's too late to say, 'We're the green government that everyone wants'."
Mr Miliband's message was that it's easy to promise the earth - no green pun intended - but if you haven't been in office, you don't know what you're talking about.
"The audience has to judge not just the scale of our promises but the credibility of them," he said.
"It's true that we don't have a fantastic record on renewables," he acknowledged, but warned that progress would be even worse under the Tories because they were not prepared to put any pressure on councils to accept wind or solar developments in their area.
Mr Miliband was rather dismissive when asked if he wanted to respond to Mr Hughes' criticism of his record.
"Not really. I think it's quite boring really. Of course, he's going to say we're terrible - that's what he does, that's what Liberal Democrats do."
But he did ask the audience to judge Labour on their plans - not their record - which is an interesting choice of emphasis.
Mr Clark accused Mr Miliband of "trying to make difference here for mischievous reasons".
"We're all agreed on the ambitions and aspirations but what's been lacking is action," he said, promising to introduce a bill in the Queen's Speech in a month or so's time, if elected, to get going straight away.
He said the Tory manifesto had "very tangible specific proposals", not "fudgy words", like having smart meters in every home by 2016.
He also said it would be undemocratic to force councils to accept wind farms, but if you get the community to have a stake in them they might actually turn out to want them after all.
Mr Clark came under fire for the number of Tory MPs and candidates that are climate change sceptics, but he insisted that wasn't a problem. Asked about one such sceptic, in particular, he said: "I don't agree with that guy, I've never heard of him."
He said it was "a function of being in Whitehall for too long" that Mr Miliband wasn't able to accept that people within parties don't all have to agree with each other.
But the other leaders did think these sceptics could be a problem. While Mr Hughes said Mr Clark was "one of the good guys" because "he had good early years education because he was in the SDP", he said Mr Cameron could struggle to pass green legislation if his own MPs didn't support him.
On Tory greenness generally, referring to Mr Cameron's visit to the Arctic shortly after becoming party leader, Mr Miliband said: "The image is fine, the huskies are great, but when it comes to confronting the real issues he is just found wanting."
Mr Johnson said he agreed that "Cameron's conversion to the green agenda was more about brand decontamination" than anything else, but called it "a sad indictment" of Labour that "even with this fairly vacuous spin they were actually outgunning you" on green issues.
While there might be some agreement, Mr Hughes said the Lib Dems stood out in terms of the scale of their vision - regional green investment banks, not just one national one, etc.
He also said that rather than a separate single section on the environment in their manifesto, green issues were woven throughout: "Look at the figures, the commitment is there."
Mr Miliband called many of the Lib Dem plans "fictional" and said that any energy policy lacking a nuclear element - as their's does - had "a massive hole" in it.
Mr Hughes, for his part, attacked Green Party leader Caroline Lucas for failing to turn up to crucial environment debates in the EU Parliament, but he drew criticism from Mr Johnson in return.
"They do like to talk green, the Liberal Democrats, but so often they like to be liked as well. They want to be liked rather than stand up and say the unpopular thing."
Mr Johnson said on planning matters "the presumption should be in favour of wind turbines", and called for "real government investment" of billions of pounds right now in order to bring about change in a very short space of time.
His message again and again was that the Greens finally have a chance of winning some Westminster seats and to do so would be good for democracy and the green agenda.
He said he was "itching" to get into the Commons and keep a close eye on whoever wins the election, to see they don't ignore the big green elephant any more.