A foreign superweed which can even grow through pavements is rampaging across Britain.

Japanese knotweed was introduced as an ornamental plant by the Victorians, but it has become the scourge of gardeners and environmentalists, growing a metre a month.

Just tiny fragments of the plant can form new shrubs, tearing through tarmac, so the uprooted weeds must be classed as controlled waste.

Now, scientists are hoping that the introduction of a small insect could halt its growth.

The sap-sucking psyllid is the Japanese knotweed's natural enemy. If it was introduced to the UK, it would be the first time the process of biocontrol has been used to control a plant species in Europe.

Once out in the wild, the new species would sustain itself, so long-term control would be "effectively free", compared to the £1.56 billion bill it would cost taxpayers in chemical pesticides.

Dr Dick Shaw, who led the research for CABI, said: "Though it is more famous for its concrete-cracking ability, Japanese knotweed's impacts on our natural habitats are severe, crowding out native plants and seriously reducing opportunities for our native wildlife."

CABI has been working to stop the spread of Japanese knotweed with funding from a consortium of sponsors: British Waterways, Cornwall County Council, Defra, the Environment Agency, Network Rail, South West Regional Development Agency and the Welsh Assembly Government.

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