Anti-blood sports campaigners have criticised plans to stage a nationwide mass shoot by gamekeepers saying the idea is "obscene".

Protesters claim thousands of wood pigeons, magpies and jays, will be killed on Saturday as up to 8,000 gamekeepers take part in the mass culling of birds across England and Wales.

The shoot, organised by the National Gamekeepers Organisation, will also record every wood pigeon seen and shot throughout the day in an attempt to find out how many birds are killed in the event.

There are around 18 million wood pigeons across the country, double the number 25 years ago, and the National Farmers Union estimates the bird costs farmers more than £4mn in crop damage each year.

The NGO says the mass shoot has been organised to control a serious pest which does a great deal of damage to farmers' crops.

But Janet Smart of the League Against Cruel Sports said many birds would be killed unnecessarily and making a day out of mass killing was "obscene in any civilised society".

A spokesman for the NGO defended the plans and said: "This form of pest control has always gone on. The only different thing this year is that we are organising to do it on one day.

"It is really an attempt to make the shoot more efficient by keeping the birds on the move."

Farmer Michael Wagstaff said: "For the crop damage the birds do to the rape, the wheat, the barley and other cereal crops, they are just vermin and need to be controlled."

But Britain's biggest shooting group is against the idea.

It supports local shoots and believes a mass cull could result in tighter controls from Europe.

John Swift, of the British Association of Shooting, said: "This pest control day is ill-conceived and if we make a jamboree out of the day Brussels may force our government to be much more bureaucratic."

Royal Society for the Protection of Birds spokesman Grahame Madge said: "We believe they cannot individually prove that there is a legitimate need to control birds on that level and we are concerned it is being done as a political stunt."

Under a general licence, farmers are allowed to shoot any birds, for the reasons of pest control, which seriously damage agricultural crops.

The RSPB has registered its concerns with the Department of the Environment and said it will be watching events on Saturday to monitor whether "non-target" birds are killed.