More money would be raised from "green" taxes under a Tory government, shadow chancellor George Osborne has said.
George Osborne is speaking about green issues on a visit to Japan
He told the Financial Times he was "completely open-minded" about the measures he would bring in, but it was clear more revenue should be generated.
He will ride on a magnetic train during a trip to Japan, and said such trains could "virtually eliminate domestic flights" if brought into the UK.
Environmental campaigners have been pressing for new taxes on aviation.
Mr Osborne would not specify exactly how he would increase the proportion of revenue taken from "green" taxes during an interview with BBC Radio 4's Today programme.
"Of course there are different options. You can tax cars - we've already got fuel duty and vehicle excise duty," he said.
"There's the whole issue of taxing aviation. There are things like landfill taxes; there is the climate change levy, which I think should be replaced by a carbon levy on industry."
He went on: "This is completely the opposite direction to the one Gordon Brown has taken us in.
"He has reduced, as Chancellor, the share of tax take that is taken by green taxes, and we want to head in the other direction."
The economic secretary to the Treasury, Ed Balls, responded by claiming the tax burden had fallen in recent years due to the government's policy of "freezing fuel duty every year because of the very high level of oil prices".
"I think the question George Osborne failed to answer is: is he really saying that he thinks taxes on motorists should be going up now at a time when petrol prices are so high?" Mr Balls told BBC Radio 4's The World at One
A magnetic train in Shanghai carries passengers from the city's airport
"If you are going to be a serious opposition you need to come along and say what are your proposals, how would you pay for them.
"Until then people won't take you seriously."
Liberal Democrat environment spokesman Chris Huhne said it was "flattering that the Tories are moving towards the Liberal Democrat position of supporting a rise in green taxes to change behaviour, but they still haven't proposed a single specific measure".
Magnetic trains, which can reach speeds of up to 360mph (580km/h) were "not science-fiction", said Mr Osborne.
"There is already a railway up and running in Shanghai. In Tokyo, I'm going to see a test train.
"They call it a test train but actually, they've already had 100,000 people go on it - and Germany is looking at it as well.
"So our leading competitors in the global economy are investing in this technology, developing this technology and running it.
"And I suppose the question is: why are we closing our minds to this kind of thing? Why do we think Britain shouldn't have this kind of thing as well?"
Asked how a Conservative government would fund such a transport method, Mr Osborne said it would be important to begin on a small scale.
"If you started with a discreet route from, say, Glasgow to Edinburgh or Manchester to Liverpool, then it would be more manageable in terms of costs."
But the vice-chairman of the Institution of Mechanical Engineers, Cliff Perry, claimed the trains used too much energy to be considered a sustainable form of transport.
The method "doesn't achieve fast journeys without an environmental cost", Mr Perry told the Today programme, as the trains "consume an awful lot of energy".