Gray squirrels are facing extermination in Britain — through genetic engineering.

The woodland pest is being targeted by the scientists who cloned Dolly the sheep.

They want to implant a gene into thousands of males to ensure any female offspring are infertile.

The trait would slowly spread, making squirrels unable to breed and wiping out the population.

Andrew Kendall, spokesman for the Roslin Institute in Edinburgh, said: “We want to reverse the invasion. It is very humane — there is no need for trapping or shooting — they just stop reproducing.”

Gray squirrels were imported from the US by rich landowners in the 1800s.

They carry a virus which has almost wiped out native red squirrels, they attack songbird nests and stop trees growing by stripping bark.

There are 2.5 million in Britain and attempts to control them have failed.

Gene editing has been called a humane alternative and could be used to rid Britain of other invasive species, such as mink and muntjac deer.