Boris Johnson has been accused of failing to take seriously the plight of pig farmers who face the prospect of having to cull tens of thousands of healthy animals due to an acute shortage of butchery and abattoir workers.

Farmers have warned that up to 120,000 growing animals will have to be slaughtered on farms and then incinerated because they cannot go to the abattoir and they have nowhere left to house them.

Despite recent media reporting on the issue, the Prime Minister appeared to be unaware of the problem when he was questioned on BBC’s The Andrew Marr Show.

His initial response was to tell the presenter: “I hate to break it to you but I am afraid our food processing industry does involve the killing of a lot of animals. I think your viewers need to understand that.”

When it was pointed out to him the whole problem was that they could not be sold for food and they would have to be disposed of on the farms, he accused the presenter of “trying to obfuscate”.

He added: “The great hecatomb of pigs that you describe has not yet taken place, let’s see what happens.”

For Labour, shadow environment secretary Luke Pollard said his comments showed ministers were “out of touch” with the problems of a key industry.

“The Prime Minister needs to take this seriously,” he said.

“The Government’s incompetence and chaotic lack of planning is about to lead to the biggest peacetime cull of pigs. This cull is a disaster for pig farmers and risks Britain’s food security.”

Nick Allen, chief executive of the British Meat Processors Association, said that while the industry was working hard to avoid such an extensive cull, farmers were facing “extremely difficult circumstances”.

“It is heart-breaking. It is an incredibly distressing situation to find yourself in,” he told the PA news agency.

“You are doing your best to look after the animals even though they are growing, you are running out of pens, you are running out of space and you have a massive cash flow problem. It is a nightmare scenario.”

He said the problems were down to the refusal of Home Office to allow in skilled workers from abroad to address the labour shortages.

He dismissed suggestions by ministers that the real issues were a lack of investment and an unwillingness to pay high enough wages to attract British workers.

“The idea that we have just been dependent on cheap labour, we haven’t been investing in infrastructure, is utter nonsense,” he said.

“It is lot more complicated than that. Even though we have increased wages quite dramatically, we are still not getting people wanting to do that job.”