Joe Hockey has ridiculed a suggestion that Australia is one of highest emitters of greenhouse gases in the OECD, despite the fact that it does top the OECD rankings of greenhouse gases per capita.

“The comment you just made is absolutely ridiculous,” the treasurer said in an interview with the BBC when it was suggested to him that Australia was among “the dirtiest, most greenhouse gas-emitting countries in the OECD group of developed countries”.

“We’ve got a small population and very large land mass and we are an exporter of energy, so that measurement is a falsehood in a sense because it does not properly reflect exactly what our economy is,” Hockey said.

“Australia is a significant exporter of energy and, in fact, when it comes to coal we produce some of the cleanest coal, if that term can be used, the cleanest coal in the world.”

The latest OECD greenhouse gas emissions index, released in January, ranks Australia as the highest emitter per capita, with Luxembourg second, followed by the US and Canada.

Luxembourg reaches such a high position on the list because its low fuel taxes mean motorists from neighbouring countries drive over the border to fill up their cars. The study found Australia emitted nearly 25 tonnes of carbon dioxide per person in 2010.

Emissions released during the process of mining coal and gas are counted towards Australia’s total, but the emissions when the fossil fuels are exported and burned are counted in the country that buys them.

So-called fugitive emissions from mining have been the fastest growing source of Australian emissions in recent years, according to the national greenhouse gas inventory, but still account for only about 8% of Australia’s total.

Australia also lags when it comes to cutting greenhouse gas emissions over the past two decades, according to the OECD data.

Of the 34 nations, only Chile, Mexico, Korea and Turkey have increased their emissions more than Australia since 1990, while the UK, France, Germany and Italy all achieved cuts in that time.

The shadow environment spokesman, Mark Butler, said what was really ridiculous was “that Australia’s treasurer doesn’t know this about Australia”.

“The nation’s most senior economic leader has embarrassed himself on international TV over a fact most school students would know,” Butler said.

Hockey angered conservationists in May when he said he found the wind farms he passed when driving between Canberra and Sydney “utterly offensive” and a “blight on the landscape.”

Last month he clarified that it had been a comment about “aesthetics”.

“I drive from Sydney to Canberra on Sundays to go to parliament and I just look at those wind farms around Lake George and I’m just appalled at a beautiful landscape ruined,” he said.

“Just for all the ‘greenies’ in the audience, if they built a huge coal-fired power station there, I would be equally appalled. So, it’s just an aesthetic view.”