In a battle to save Britains indigenous red squirrels, the government said Friday it was looking into a possible mass sterilisation programme for their disease-bearing grey squirrel rivals.

The agriculture ministry's Animal and Plant Health Agency told AFP in a statement it would "look at the feasibility of using oral contraceptives" and would initially work on developing a "suitable bait".

The Times newspaper reported that contraceptives could be concealed in chocolate spread and would reduce numbers by more than 90 percent from 3.5 million.

The decline of the red squirrel population, which is now largely confined to parts of northern England, Scotland and Ireland and numbers around 140,000, has been an issue in Britain for many years.

Grey squirrels, which are native to North America, were first introduced in Britain in the Victorian era but quickly gained the upper hand.

The particular danger of grey squirrels is that they spread the squirrelpox virus, which does not affect them but quickly kills off red squirrels.

Even heir to the throne Prince Charles, a well-known environmentalist, has taken up the cause with passion, heading up the Red Squirrel Survival Trust.

The prince hosted a reception at his Clarence House residence on Monday for the United Kingdom Squirrel Accord, a grouping of woodland, timber industry and conservation organisations set up in 2014.

"The Prince of Wales is committed to protecting the red squirrel across the UK and created the Squirrel Accord in order to address this issue," a spokeswoman for Clarence House said.

"However, the grey squirrel fertility control research and its funding is not something the Prince of Wales or his charities are directly involved in," she said.

The Times reported that Charles "favours the idea" of sterilisation as a humane alternative to culling.