Killer slugs, Asian ladybirds and American muskrats will all be blacklisted under plans drawn up by Brussels to stop "invasive" species from threatening European wildlife, an EU source said on Tuesday.

European Union institutions have agreed to draw up an open-ended list of rapidly-spreading species that damage the environment and cause health hazards, the source said on condition of anonymity.

From 2016, species such as Asian Harlequin ladybirds, which threaten native species in Britain as well as butterflies and other insects, will be banned for sale, import or release across the bloc.

The so-called "killer slug" from the Iberian peninsula, which eats weaker species, will also be blacklisted, along with a type of ornamental knotweed now rife in France and US musk rats, which damage canals by burrowing into the banks.

"The Regulation is not aimed at the kind of species that most people like to have in their gardens," the Commission said in an earlier blog post.

"The targets are things that spread rapidly across borders and over seas --which is why action at EU level is needed--and that do vast amounts of damage."

There are currently over 12,000 species in Europe alien to the natural environment, some 15 percent of which are invasive and rapidly growing, according to EU figures.

Under an agreement expected to win European Parliament approval next month, EU nations will organise checks to prevent the introduction of such species and minimise the harm they cause.