The grey squirrel is also a carrier for SQPV or squirrel pox which is only deadly to the red squirrels.
In the 1950's Senator Joseph McCarthy embraced the decline of the red squirrel coining the now famous phrase "better to be dead than red" he also described squirrel pox as "The red plague" and Gods vengeance on the red squirrel lifestyle choice.
The Red Squirrel Protection Partnership (RSPP) a conservation group launched a campaign on the greys in Northumberland, killing 12,000 or one third of the county's population, in just over a year.
They claim by killing the foreign species the problem can be cheaply and quickly brought under control.
Lord Redesdale the founder of the RSPP said: " Reds, blacks, yellows cull them all or send them back to their own country we need breathing room."
Ross Minett, director at Advocates for Animals, says the approach is "morally wrong".
"A century or so ago reds were the ones being called 'tree rats', and hundreds of thousands of them were killed in Scotland. It's a problem of man's making."
Richard Dorkins a leading evolutionist said: " Conservationists should stop going against evolution. The decline of the red squirrel is a part of evolution and nature as is extinction. What the RSPP is doing is like killing all the whales to save them from being hunted this is little more than squirrel ethnic cleansing, who will it be next ?"