Live something from an old B-movie, alien species such as "killer shrimp" and zebra mussels are invading Britain at a rate never seen before.
The Environmental Audit Committee, Parliament's green watchdog, has warned the government that Britain needs better prevention, monitoring and eradication measures to fight non-native plants and animals that threaten the environment and human health.
In 2012, 1,875 non-native species were counted in the UK, 282 of which had become "invasive."
The likes of Japanese Knotweed, North American signal crayfish, killer shrimp, and zebra mussels, can have a detrimental effect on the native species they supplant, as well as on human health and business, the committee heard.
Other non-native species in Britain include the grey squirrel and rhododendrons.
A species is defined as native in Great Britain if it re-colonised after the end of the last period of glaciation.
Joan Walley, chair of the committee, said more non-native species were being seen in Britain than ever before.
"Not all of these species will become 'invasive', but the ones that do can harm native wildlife, clog up our waterways, cause costly problems for homeowners and sometimes even harm human health.
"It is too expensive to control or eradicate all invasive species, so we have to be smart and pick the fights that we know we can win. We may just have to live with grey squirrels and rhododendrons in much of the UK, but we can and must control other invasive species - like the killer shrimp devastating eco-systems in our rivers and lakes."
The committee is calling for a change in the law to give the government new powers to eradicate invasive species before they become established.
The Wildlife and Countryside Act 1981 prohibits the release of non-native animals and plants into the wild, but no-one has ever been prosecuted under the law.
It is believed that some non-native animals can also cause widespread change to native species, such as the replacement of the red squirrel by the grey squirrel over most of Britain. Grey squirrels cause £10 million a year in damage to trees, estimated the Country Land and Business Association (CLA)
The European Environment Agency estimates that invasive species cost EU countries £9.9 billion a year, while it cost £11 million to eradicate Rhododendron from one national park in Wales alone, according to the CLA.
Some invasive species have direct human health effects. Anglers coming into contact with giant hogweed have received skin inflammations, while the pollen of common ragweed causes asthma. The Asian hornet, which has yet to enter Britain, has killed six people in France.
The Asian hornet, distinguished by its yellow feet, is smaller than the native hornet in Britain. Its toxic sting can cause death through anaphylactic shock and kidney failure. There is a high likelihood that the hornet will enter Britain through soil from imported plants or by flying across the Channel.
A spokeswoman from the Department of Food, Environment and Rural Affairs (Defra) said: "This report recognises we have the most advanced approach across Europe in tackling the threat of invasive non-native species, helping identify and prevent the spread of plants and animals that don't belong here.
"Through targeted surveillance, working with industry, voluntary groups and the public as well as strict controls at the border, we are able to take swift action on the ground, including eradication, or if not possible, containment.
"We keep our approach under review and are working with European partners on measures to strengthen the response across borders."