Diners at Otto’s know what to expect. Roasted duck flambéed in brandy and carved at the table. Lobster bisque, concassé. Escargots à la bourguignonne. And the epitome of French fine dining, foie gras.

As the maitre d’ applies himself to constructing an order of tartare de boeuf, Otto Tepasse, the proprietor, considers whether foie gras has a future in Britain. New York’s authorities have decided to ban shops and restaurants from selling it and campaigners want London – indeed, the whole of Britain – to follow suit.

“Banning it is a fad,” he says. “New York is just following a fad, going with the flow. If it is ethically raised, then I don’t see a problem. If they are [forcibly] fed on an industrial scale, I think that’s wrong. But the foie gras we serve comes from a family who look after their geese.”

His stance is not one that most animal welfare campaigners agree with. Making foie gras generally relies on force-feeding ducks or geese for about two weeks, causing their livers to expand dramatically. Some farmers claim force-feeding – known as gavage – is unnecessary, but in France, where 98% of the foie gras eaten in Britain is made, a pâté can only be called foie gras if gavage is used.

Campaigners say the funnel or tube used during gavage is painful and can be fatal on its own, and that the birds become fearful of humans and spend their final days in suffering. Tepasse, who prides himself on knowing where every slice of meat in his restaurant came from, believes the foie gras he serves is ethically produced, since gavage is only done by hand.

“Three years ago we had 50 or 60 people outside the restaurant, three or four nights a week. It was awful,” Tepasse says. “Shouting with megaphones, sirens. I was the only place in London that stood up to them.”

He refused to remove foie gras from his menus, and after five months the protests, organised by Direct Action Everywhere (DxE), died down. He was rewarded by the French ministry of foreign affairs, who hosted an event last year celebrating him and other international supporters who have championed foie gras. Slowly the dish has returned to some of the other restaurants who were targeted, although few were prepared to discuss the issue publicly.

Animal rights protesters demonstrating in New York this summer. Photograph: Angela Weiss/AFP via Getty Images

But the pursuit of a ban in the UK continues. British farmers are forbidden from producing foie gras under animal welfare legislation, but the UK imports about 180 to 200 tonnes a year. Campaigners and politicians say EU single-market rules mean the UK cannot ban imports, but Brexit would change that. They are encouraged perhaps by the fact that Carrie Symonds, Boris Johnson’s partner and a vocal environmental campaigner, is patron of the Conservative Animal Welfare Foundation, which has called for imports to be ended after Brexit.

Labour is pledging to ban foie gras imports “at the first available opportunity”, Sue Hayman, the shadow environment secretary, says. “Foie gras production is an exceptionally cruel practice,” she says. “The excessive force-feeding of these birds inflicts serious injury and stress upon them and cannot be justified as a method of food production.”

Conservatives such as Henry Smith, MP for Crawley, agree. Smith led a Commons debate on foie gras last year during which environment minister George Eustice said Brexit would present an opportunity to “look at restrictions on sales”.

“I very much advocate what other jurisdictions have done in places like New York and California,” Smith says. “It’s a very cruel, outdated practice and I think there is a broad majority in the UK opposed to it.”

In July a YouGov poll on behalf of the campaign group Animal Equality found fewer than one in 10 people had eaten foie gras in the last year, and 79% of those expressing an opinion supported a ban, with 150,000 people signing a petition against foie gras imports.

The acting executive director of Animal Equality, Abigail Penny, says foie gras is “unspeakably evil” and can never be produced ethically.

“Every year millions of ducks and geese suffer in unimaginable ways to produce this vile ‘delicacy’. Force-feeding can never be cruelty-free,” she says. “Our investigations have shown that these innocent animals are often kept in dirty, dismal cages, packed in tightly with many other terrified ducks and geese. Many suffer painful sores on their feet from the wire floor and other injuries are often left untreated. The process is so brutal that the UK has banned the production of foie gras, yet we still import this product. This hypocrisy must end.“

Fortnum & Mason says ‘people should have the freedom to choose whether to buy it or not.’

Even leaving the EU might not guarantee that the UK could ban foie gras imports, some trade experts say. Post-Brexit, the EU might dispute a ban under World Trade Organization rules and some attempts to ban meat on animal welfare grounds have been rejected. David Henig, director of the European Centre For International Political Economy, says there are concerns that a ban would not be compatible with WTO law, but adds that the issue has not been fully tested.

Given the pressure on restaurants from activists such as DxE, is a ban necessary? Very few restaurants and suppliers were prepared to admit that they sold foie gras. Most restaurants either did not respond or said they were worried about attracting attention. Fortnum & Mason, which does sell it, said in a statement that there was a “large market” for foie gras and that “people should have the freedom to choose whether to buy it or not”.

None of the main online retailers that sold foie gras were prepared to speak publicly, although one said that the anti-foie gras lobby was “intolerant”. “People don’t have freedom any more. It is becoming crazy. We are like in a straitjacket.”

Yannis Alary, managing director of Blanchette in London, says his restaurant took foie gras off the menu after protests three years ago. “It was a nightmare. One of my guests almost had a fight with them. To be honest, I’m worried what’s going to be next. In a few years, will we have people saying ‘stop selling meat’? I think it’s gone too far.”

There are similar questions being raised over veal, octopus, lobster and crab, as well as factory farmed chicken. For Tepasse, “people should be more discerning about food. How can someone buy a chicken for £2? That’s wrong – food should be more expensive.” He even thinks that mass-produced foie gras could be banned in the UK. “But not if it is done properly. And I won’t be bullied.”