This article states that "CONTRACEPTIVES could soon be used on rabbits, foxes and kangaroos to cut the population of rural pests.

But the idea has opponents worried about genetic consequences.

Some scientists see the "Pill for pests" as a humane alternative to widespread slaughter, and this includes using immuno-contraceptive vaccines to control native species, such as kangaroos and possums.

But one scientist said work on immuno-contraceptives for native animals should be banned because they could be unethical or unpredictable.

"It's in the research phase, which is why I'm jumping up and down now," said Des Cooper, of Macquarie University's Biological Sciences department.

Professor Cooper said an institution he worked for, the Marsupial Co-operative Research Centre, should cease such research.

"I strongly object to the use of it on Australian native animals because I don't think we can predict what will happen," Professor Cooper said.

"I think we will change their genetic structure, leading to unpredictable results as far as their capabilities for fighting diseases."

Scientists are developing immuno-contraceptive vaccines to attack the animal's sperm or egg.

The vaccine would be delivered in genetically altered maize, carrots or potatoes, or by genetically modified bacteria or virus.

Professor Cooper said the vaccines would not work on some animals but survivors would reproduce and alter the genetic structure of the species.

Rabbits alone cause a $600 million loss in agricultural production each year; while 15 species of mammals have become extinct since foxes were introduced to Australia. The vaccines could eventually be used by humans in developing countries.

Molecular biologist Michael Holland acknowledged Professor Cooper's concerns but said he was taking an extreme view.