A POISONOUS invasive weed which can cause third-degree burns is spreading along the River Aire towards Bradford and has already reached Bingley, the Telegraph & Argus can reveal.

Giant hogweed grows up to 16ft high and a toxin in its sap makes skin super-sensitive to sunlight and contact can can cause blisters, permanent scarring and even blindness if sap enters the eyes.

Its long lasting effects can also mean victims have to avoid sunlight for years after contact.

Imported from southern Russia in the 19th century as a garden novelty, it is now spreading across the country with a recent spike in reports of children and walkers being injured by innocent contact with Heracleum mantegazzianum, as it is officially known.

It has colonised riverbanks, verges and wasteland and is now known to be established between Cononley and Bingley, said Aire River's Trust spokesman Kevin Sunderland.

"This is very bad stuff and it's now got as far as the island between Bingley's Ireland Bridge and the weir," Mr Sunderland said.

"The Environment Agency had to destroy a plant on the island last week. We've found it at Cononley and it's spread all along a stretch beside the trunk road at Steeton.

"A plant was also found where Bingley Congs cricket club runs down to the river and I rather suspect there's a lot around Marley, because the riverbank's like a jungle down there.

Mr Sunderland said a single plant can produce 80,000 seeds from its huge crown of tiny flowers.

"It's the biggest herbaceous plant in Britain and they spread by air, but they really succeed when seeds get into the river and are carried downstream before settling in the muddy banks," he said.

Giant hogweed needs to be destroyed before seeding takes place and this can be done by high-strength weed killers or cutting it down.

"I'd appeal to people to help spot it as we need volunteers to monitor areas all the way to Bradford," Mr Sunderland said.

An Environment Agency spokesman said: “We have been working closely with our partners to help to eradicate this highly invasive species from the Aire catchment.

"Giant hogweed has spread across the country since it was introduced into Britain in the early 19th Century as an ornamental plant, and its size and toxic nature has a real impact on the areas where it is growing.

"Our operational teams have been spraying the plant to prevent it from spreading further. Spraying is particularly effective when the plant is caught early.

"The public can help prevent the spread of giant hogweed by controlling it if it is on their land, and ensuring that any contaminated soil or cuttings are dealt with carefully. Safety precautions must be taken, though, because the plant’s toxic sap can cause burns and blistering on the skin."