“They are our main competitors. We're taking them very seriously,” said Jörg Meuthen, who headed the AfD's European elections list.
The Greens stole a march on the AfD in Sunday's vote, doubling their share from the last European elections to just over 20 percent and coming in second after Chancellor Angela Merkel's centre-right alliance.
In comparison, the AfD, which had styled itself as the champion of diesel car owners and coal mines, obtained only 11 percent — underperforming its 2017 national elections showing.
On Monday, Meuthen derided the Greens as “rabbits that will make smaller and smaller hops because at some point, a test will come and it will be devastating.”
“They are not conservationists, what they do with their wind technology and such is an obvious destruction of nature,” he charged.
The AfD leader also hit out against those who call his party climate change deniers, as he claimed that “it is not about denying man-made climate change, but about data that is not certain.”
“I'm saying we have doubts and I would like the so-called climate policies to allow for doubts, allowing for a greater margin of error.”
Under the 2015 Paris deal to limit global warming to well below two degrees Celsius above pre-industrial levels, the 28-nation EU has pledged to cut greenhouse gas emissions by at least 40 percent by 2030, compared with 1990.
But many scientists and climate activists warn that unless major economies sharply raise their ambition, the Earth is on course for catastrophic warming.
The UN Intergovernmental Panel for Climate Change warned in October that warming is currently on track towards a disastrous 3C or 4C rise.