If you announce on Facebook that you're having a baby, don't expect Les Knight to be among the well-wishers.

The self-described "finder" of the provocatively-named Voluntary Human Extinction Movement — or VHEMT (pronounced "vehement") — says congratulating people on a pregnancy is an example of "natalist propaganda".

"If someone announces on social media that they're expecting, everybody's going to say congratulations," Mr Knight told RN Drive's Patricia Karvelas.

"If somebody says 'we decided not to procreate', there's going to be a lot of silence there.

"I think congratulations is more in order when people decide to save eight-and-a-half hectares of potential wildlife habitat for 82 years, which is what someone in Australia who chooses not to add another to the population can achieve."

What is VHEMT?

Sorry, this audio has expired The Voluntary Human Extinction Movement

Mr Knight says the movement is designed to make people think twice about having children.

"Many people assume that it's what they're going to do, it's the default," he says.

"If people really think about it before they procreate, they're likely not to — more and more people are choosing to not procreate these days."

VHEMT's motto is "may we live long and die out", and its stated aim is to phase out the human race by encouraging people to stop breeding.

The VHEMT website says it is "a movement advanced by people who care about life on planet Earth".

"We're not just a bunch of misanthropes and anti-social, Malthusian misfits, taking morbid delight whenever disaster strikes humans," its FAQ says.

"Nothing could be farther from the truth. Voluntary human extinction is the humanitarian alternative to human disasters."

VHEMT denies being anti-human, but believes the Earth would be better off without humans. ( Istockphoto )

Mr Knight says the world would be better off with fewer humans.

"We would be more likely to provide for everyone, we would stop encroaching on wildlife habitat," he says.

He admits a "voluntary extinction" of humanity is unlikely, but says "it would only be fair".

"We're causing the extinction of maybe a million other species," he says.

"The odds on our success are about the same as the odds on us taking care of 10 billion people in the future.

"About 30,000 [people] die every day of preventable causes, so it's not a good situation."

Babies the result of 'indoctrination'

Mr Knight denies that the fact animals reproduce in the wild is proof that having children is a natural urge.

"What they're doing is engaging in activities that lead to procreation, same as us," he says.

"We have instincts, or urges at least, that cause us to engage in [sex], but the actual instinct to procreate is actually a cultural indoctrination."

He says there are parents who have joined his movement.

"The idea is to not produce more than we already have, and that helps us to be able to take care of the people who are already here," he says.

The US-based activist says he is for "reproductive freedom" and is not in favour of government intervention such as China's former One Child Policy.

He says nearly half of all pregnancies in Australia and the US are unintended, which implies people aren't getting adequate access to contraception.

"In other places, no contraception is available at all, and they like to not procreate but they're denied that access," he says.