The Wildlife Trusts is calling for tighter dairy controls amid slurry and river pollution concerns
The NFU has challenged criticism of large dairy farms, warning that tougher environmental rules based on herd size could unfairly penalise producers without tackling the underlying causes of agricultural water pollution.
In a response published on Tuesday (20 October), NFU dairy adviser Amy Mepham argued that farms should be judged on their environmental performance rather than their size, questioning calls from the Wildlife Trusts for tighter regulation of intensive dairy operations.
The dispute follows the conservation charity's Doing Dairy Differently report, which warned that the growth of large, permanently housed herds was increasing pressure on rivers, soils and wildlife.
Environment Agency figures show dairy activity accounted for 187 of the 263 serious or significant agricultural water pollution incidents recorded at non-permitted farm sites in England between April 2021 and March 2026.
That represents approximately 71% of the total, although the figures do not establish whether larger dairy herds are more likely to cause pollution than smaller operations.
The Wildlife Trusts' report, published in September, identified more than 40 so-called 'mega dairies' across the UK, with the largest housing approximately 2,600 cows.
It also warned that the number of intensive dairy farms keeping cattle indoors throughout the year had more than doubled over the past decade, increasing the volume of slurry requiring storage and management.
The charity is calling for environmental permitting to be extended to higher-risk dairy operations, including very large housed units and farms with little or no grazing.
However, the NFU argues that a broad permitting regime could impose significant costs without adequately reflecting differences in farm management, infrastructure and environmental risk.
Mepham said: "British dairy farmers are not obstacles to environmental progress; they are essential partners in delivering it."
She maintained that environmental performance depends on factors including slurry storage capacity, nutrient management, available land, local geography and day-to-day farming practices.
The union accepts that serious pollution incidents must be addressed but says the available data do not establish a direct relationship between herd size and environmental damage.
The Environment Agency's latest figures show serious and significant agricultural water pollution incidents across all farming sectors fell from 72 in 2024/25 to 48 in 2025/26.
However, the regulator said there was no discernible downward trend across the five-year period, with failures in slurry storage infrastructure and drainage responsible for many incidents involving dairy farms.
The financial implications of further regulation are also raising concerns within the sector.
An NFU survey published in July, involving nearly 700 dairy farmers, found that 70% of respondents planned future infrastructure investment.
However, nearly 60% identified access to capital as a barrier, while 32% cited planning constraints.
The findings highlight difficulties facing producers seeking to improve slurry storage, drainage and other environmental infrastructure while managing tight margins and investment costs.
The NFU also points to the industry's Sustainable Dairy Pathways report, which estimates approximately £2.4 billion of investment will be required across the dairy sector to achieve its sustainability ambitions by 2030.
Much of that investment would be directed towards slurry and manure management infrastructure and energy improvements.
Meanwhile, the Wildlife Trusts argues that stronger regulation must be accompanied by greater financial assistance, practical advice and support for pasture-based, organic and regenerative dairy systems.
Gemma Lane, land use policy manager at the Wildlife Trusts, said when its report was published: "The UK government must extend environmental permitting for intensive dairy & beef farms so that their impacts can be properly measured and managed."
The charity also wants improved nutrient planning and greater support for farmers investing in slurry storage and pollution prevention.
The NFU maintains that the dairy industry has already made environmental progress, pointing to improvements in productivity, animal nutrition, genetics and resource efficiency.
Figures cited by the union show Great Britain had approximately 6,850 dairy producers in April 2026, with an average herd size of 175 cows.
Greenhouse gas emissions per litre of milk have fallen by around 22% since 1990, according to figures highlighted by the NFU.
The disagreement comes as Defra considers extending environmental permitting arrangements, already used for intensive pig and poultry farming, to dairy and intensive beef operations in England.
Such a system could bring additional inspections, monitoring, record-keeping and compliance requirements, depending on how any future rules are designed.
The NFU is urging ministers to ensure changes are proportionate and based on measurable environmental risks, while calling on processors and retailers to help fund improvements through fairer returns.
Both organisations support action to reduce pollution, but differ over how higher-risk farms should be identified and how additional controls should operate.
For dairy producers, the debate raises questions over the investment, monitoring and regulatory requirements that could accompany future efforts to improve water quality.