He is co-author of a book on the population topic, Overloading Australia, which Dick Smith sent to every federal and state politician, and every mayor.

But with the major parties continuing to ignore population - what his Stable Population Party considers ''the everything issue'' - Mr O'Connor, who also works as a marriage celebrant, is throwing his hat in the ring, running as a Senate candidate for the ACT.

''Until I was 30 I assumed there were old geezers somewhere who worried about the world … I think a lot of young people are that way,'' the 68-year-old said.

''By the time they're out of that phase they've got a family and their noses to the grindstone, so a lot of these groups, it's retirees who power [them].''

It's one of many things the older generation are good for, he says, dismissing the notion that population growth is necessary to counter the ageing population.

''They're raising this huge fear that there will be three times as many people over 65. But the point is that there are going to more people over 65, but there will be fewer people under 20, and the young are actually the most expensive in the population,'' he said.

''Not only do they not produce anything themselves until such time as they finish their studies, but they pull other people out of employment - and they need constant minding. Very few old people need to be minded all the time.''

There is plenty of economic theory to back up the objection to the Big Australia we are heading towards, with current growth at 1.7 per cent, a trajectory to 40 million by 2050

Mr O'Connor points to US economist Lester Thurow's estimates that spending 12.5 per cent of GDP is required to expand infrastructure capacity by 1 per cent a year, or about $200,000 per extra person.

Against that necessary infrastructure spending, Treasury's 2010 Intergenerational Report estimated 4.1 per cent of GDP would be needed for extra health and aged care, albeit using the figure of 35 million by 2050.

''Our [growth] levels are bizarre by First World standards,'' Mr O'Connor said. ''Indonesia is 1.2 per cent - and actively trying to reduce it.

''[The birth rate] is just below two, which is exactly where it ought to be for Australia - nice, even-sided generations with some scope to bring in an excess of immigrants over emigrants,'' O'Connor said.

The problem, he said, was the ''very powerful business lobbies'' that want higher immigration levels to create new markets and fill jobs with cheaper labour.

''Refugees are not the problem,'' he said. ''They're still just 5 per cent of the intake. You could double refugees if you wanted to and still reduce the immigration intake enormously. There's no reason we are seeking this huge intake of people. Most First World countries are stable populations and the claim it makes you richer isn't true either - the world per capita wealth table is dominated by countries under 10 million - most of the Scandinavian countries, for instance.''

While Mr O'Connor is not optimistic about his own chances of election, he thinks the issue is gaining traction, and the electorate deserves a choice.

''Every nation has both a right and responsibility to keep its population in balance with its resources. The notion that you can grow forever is crazy economics.''