CLIMATE change could help an invasive weed known to trigger severe allergy attacks gain a foothold in Britain, experts warned yesterday.

Ragweed (Ambrosia artemisiifolia) is native to North America but since the 1960s has spread rapidly across warmer parts of Europe.

The notorious plant is still rare in Britain but, by 2050, it could be scattering pollen across much of England, causing new levels of hay fever misery to susceptible individuals, new research suggests.

Pollen from the weed not only induces severe allergic reactions but also extends the hay fever season from summer to autumn.

Last year, researchers from the University of Leicester recorded airborne ragweed pollen levels in the East Midlands high enough to cause significant hay fever attacks.

The weed is a far more potent allergy trigger than grass and experts fear it could pose a serious public health problem if it became established.

Scientists writing in the journal Nature Climate Change found that predicted levels of global warming were likely to create conditions favourable to ragweed across large areas of northern Europe, including Britain.