London, Dec 15 (IANS) Rabbits, introduced to Britain by the Romans, have cost the country more than 260 million pounds a year in damage to crops, businesses and infrastructure, according to a research released Wednesday.

According to research done in England, Wales and Scotland by CABI, an international agriculture and environment organisation, the estimated 40 million rabbits in Britain have been named the ‘most costly invasive species’ in the country, the Guardian reported.

Japanese knotweed, introduced in the mid-19th century as an ornamental garden plant, clinches the second spot with 179 million pounds as it poses its own costly threat to the economy while it colonises roadsides, riverbanks and derelict land.

The total cost of such invasive species has now reached 1.7 billion pounds a year to the English economy, more than 250 million pounds in Scotland and 133 million pounds in Wales.

But the report also provides justification for the high cost of controlling non-native species.

It has been estimated that the current eradication programme for water primrose, a group of South American aquatic weeds which block waterways, will cost 73,000 pounds a year – significantly less than the estimated 242 million pounds it would cost if the weeds were to become widely established as they have in countries like France and Belgium.

Other invasive species that complete the top 10 are the common field speedwell or wild oat at 100 million pounds, rat at 62 million, potato cyst nematode at 50 million, non-native deer at 35 million, varroa mite (a parasite of bees) at 27 million, floating pennywort at 25 million, house mouse at 18 million and grey squirrel at 14 million.