Parliament must “seriously consider” levying a tax on meat to reduce greenhouse gas emissions and help to render the farming industry carbon neutral, the Green party MP, Caroline Lucas, is urging.

She will say on Friday that a meat tax in the UK could be offset for more sustainable meat producers, such as organic livestock farmers, through more money for sustainable agriculture schemes.

Lucas will tell the Oxford Farming Conference, an annual gathering of farmers from across the UK, that the country must prioritise “more humane and human-scale methods of livestock farming, together with support for farmers to transition to less livestock”.

“If the world’s diet doesn’t change, we simply can’t avoid the worst effects of climate change,” Lucas will say, in a stark warning timed to coincide with the push for people to adopt a vegan diet for a month, the “Veganuary” movement.

In a call likely to be controversial, she will say: “Better manure management and careful selection of feed can both help reduce greenhouse gas emissions, but – at the risk of incurring the wrath of the energy secretary, who said recently that encouraging people to eat less meat would be the worst sort of nanny state ever – we need serious consideration of measures like a meat tax.”

She said that it would take “more than motivated consumers to bring about sustainability” in agriculture. Globally, livestock rearing is estimated to be responsible for about 15% of greenhouse gas emissions.

Caroline Lucas: ‘If the world’s diet doesn’t change, we simply can’t avoid the worst effects of climate change.’ Photograph: Niklas Halle'N/AFP/Getty Images

Lucas has tabled a parliamentary motion to require farming to be net zero in emissions as quickly as possible, which would involve ways to reduce fertiliser use and increase the amount of organic matter in the nation’s soils, both issues that Michael Gove, the environment secretary, also espouses.

She said: “We need to bring the whole food chain into the circle of responsibility, not leaving farmers to work on their own, together with clear signals that society will play its part in funding this transition through a new agriculture policy.”

But the notion of Veganuary has come under attack from some at the conference, with the National Sheep Association (NSA) claiming the movement, which encourages people to give up animal products for the month and consider permanent changes to their diet for health and environmental reasons, was part of a “campaign against livestock farming”.

Phil Stocker, chief executive of the NSA, defended British sheep farming as working to improve the environment rather than causing damage to it. “Our concern is that our unique, grass-based method of sheep production in Britain is hidden within more global and general statistics,” he said.

He contrasted the UK’s sheep farming, which includes many upland areas unsuitable for other forms of agriculture and is one of the least intensive forms of livestock farming, with the megafarms and feedlots that characterise beef, pork and poultry production in many parts of the world, chiefly the US but increasingly being brought to the UK.

The National Sheep Association argues that farmers are working to improve the environment rather than causing damage to it. Photograph: Alamy Stock Photo

“We are seeing criticisms from welfare campaigners, rewilders, climate change campaigners and health campaigners – but all these are connected and ignore the fact that UK sheep farming works very much in harmony with our environment, our landscapes and our human ecology, creating a countryside the majority of the public love and producing a food product that is healthy and nutritious within a balanced diet,” he said.

Stocker said he opposed a meat tax: “The right meat, consumed sensibly, should be incentivised and not taxed. Sheep production is not damaging to the environment or to health – sheep mainly eat grass and grass is part of a complex and natural cycling of carbon, with soil storing carbon in organic matter.

“Any meat tax would be likely to affect all meat production and consumption – and there are many different forms of meat production. A meat tax would end up putting further pressure on primary producers – in the case of sheep this would impact on the profitability of many small family farms, yet these are highly desirable and deliver a host of economic, social and environmental goods.”

Earlier Gove told the conference that advances in synthetic biology meant that in the future we would be able to create traditional farming products such as meat, milk or eggs in laboratories, adding that “the potential for Britain to lead in this revolution is huge”.

But asked whether the UK should be looking into increasing its production of “fake meat”, the National Farmers Union president, Minette Batters, said: “When you have one of the very few areas in the world where you have the right climate for producing food, that surely is what you should be doing.”

She added that “95% of what we eat is produced in soil, it’s nutrient dense and that is why it is such a valuable food. Why would you want to be stepping back from that?”