The leading retailer, Marks and Spencer, has refused to rule out selling grouse shot for sport after the official hunting season opens next month.

The up-market food store has been targeted by wildlife campaigners, led by the naturalist and BBC Springwatch presenter, Chris Packham who has called on M&S to ban “toxic” grouse meat.

“Would you want to eat grouse from a supermarket anyway? I think not. They’re shot using lead ammunition,” he said.

Campaigners say they have previously found high levels of lead in grouse meat sold in another supermarket. They are now threatening to test any grouse sold by M&S.

Packham promised to boycott M&S if it sells grouse this year. He has tweeted the retailer pointing out that hen harriers and mountain hares are killed to protect grouse so there are enough to be shot.

“Do you wish in any way to support this?” he said in one tweet. “How much blood do you want on your shelves?” he asked in another.

Questioned repeatedly, an M&S spokeswoman declined to say whether or not it would be selling grouse. She also refused to name the estate with which the company is having discussions, or to provide a copy of its codes of practice.

“We are currently working with our supplier to monitor numbers for this season and will only stock grouse if the numbers are strong enough,” she said.

“Two years ago we worked with independent industry experts and the Game and Wildlife Conservation Trust to introduce the game industry’s first codes of practice to ensure all our game, including grouse, is sourced to the highest standards of game rearing and moorland management, from estates that we know and trust.”

But Packham told the Sunday Herald that he doubted whether any driven grouse moors could prove that they were environmentally sustainable. “The public no longer believe that these places are being suitably or sustainably managed,” he said, adding: "There’s no more hiding it. So something has to stop ... and because we care, we are going to do something about it. Crime is crime and in the end criminals get their come-uppance.”

Packham also challenged the Iceland frozen foods chain, which has previously marketed grouse. But it said that it had “no plans to stock grouse” this year, for which he has awarded them “top marks for environmental integrity and customer safety”.

Packham has been backed by the wildlife campaigner and blogger, Mark Avery. He said he doesn’t trust M&S any more because of its failure to answer questions about its codes of practice or lead levels in grouse.

If M&S do put grouse on sale, he promised to be the first customer. He said he would then send the meat to a laboratory to be tested for lead levels.

Avery is behind a UK parliamentary petition to ban driven grouse shooting. It has so far been signed by over 58,000 people, and he is “very hopeful” it will reach the 100,000 signatures needed to trigger a debate in the Westminster parliament.

But Packham’s intervention prompted a furious response from the shooting and landowning lobby. Four countryside groups banded together to release a joint statement calling on the BBC to “rein him in”.

Peter Glenser, chairman of the British Association for Shooting and Conservation (BASC), accused Packham of espousing an anti-shooting agenda. “This must be stopped by the BBC if they want licence fee payers to have faith in their editorial independence,” he said. “To condemn shot grouse as toxic is blatant misrepresentation.”

Grouse shooting had an economic value of around £100 million per year to the UK economy as a whole and supported the equivalent of more than 2,500 full-time jobs, he said.

Tim Baynes, director of the Scottish Moorland Group representing landowners, said: “The Food Standards Agency confirmed it has no plans to change their advice on game meat despite many ill-founded claims on the matter."

According to Tim Bonner, chief executive of the Countryside Alliance, the BBC’s editorial guidelines required that presenters like Packham must not engage in controversial campaigns. “He cannot continue to trade on his profile as a BBC presenter to pedal mistruths and propaganda,” he said.

In a statement, the BBC described Packham as a naturalist in his own right who was not solely employed by the BBC. “If Chris Packham wishes to express his personal views outside of his employment on BBC natural history programmes, he is entitled to do so,” said a BBC spokesperson.

The shooting lobby’s view, however, was dismissed by the blog Raptor Persecution UK. “This is less to do with the grouse-shooting industry’s concerns about BBC impartiality but more to do with them wanting to silence an articulate, thoughtful, well-informed and popular celebrity to prevent him expressing views on the disgraceful and damaging aspects of driven grouse shooting,” it said.