Lib Dem leader Sir Menzies Campbell has urged people to make greater use of energy efficient light bulbs - even though he does not have any himself.
Sir Menzies says people should go to the shops by bus
He made the admission as he told BBC Radio One's Newsbeat that individuals had a responsibility to do their bit to save the environment.
He pledged to replace dud light bulbs in his house with energy saving ones.
Sir Menzies also said he had given up his Jaguar car as part of his efforts to be more environmentally friendly.
Sir Menzies spoke two days after Tony Blair told the same show that people should measure how much CO2 their homes pumped out through using energy.
The prime minister also stressed that every household should have at least three energy efficient light bulbs.
When asked about what he thought the public should do to save the planet, Sir Menzies said: "We've all got responsibility.
"For example, to use public transport instead of using our motor cars, to use cars which are much more energy efficient, which have less impact upon the environment - even to use those light bulbs which are more energy efficient.
"Each of us by changing our individual behaviour can make a contribution and if we're going to get this right, we've all got to make a contribution."
When asked how many energy saving light bulbs he had in his house, Sir Menzies said: "I don't have any.
"None of the light bulbs in my house have gone out for a while, but I will be making sure when we replace them, we replace them with energy saving bulbs.
"But I tell you what I do, I make sure there are no unnecessary lights on in my house."
Sir Menzies reiterated that he had made a contribution by "getting rid of my beloved 12 cylinder Jaguar because it was no longer environmentally friendly.
"It's a wonderful, wonderful machine but it's very damaging to the environment - we've all got to make sacrifices," he said.
He stressed that he tried to use the train and Tube "as often as possibly I can", rather than flying, and his party was looking into proposals for an aviation tax which "would be levied against aircraft movements, not individuals going on holiday".
"At the moment aviation is one of the fastest growing sources of damage to the environment and there is no realistic tax regime to discourage those who operate aircraft from behaving in an environmentally friendly fashion," he said.
"It's not to stop people from flying, it's to stop aircraft flying which cause damaging emissions - quite different."
Earlier this week, the Commons Environmental Audit Committee called for an increase on tax on air travel and "gas guzzling" cars.
In their report, the MPs said other measures would be almost useless unless pollution from transport was tackled.