Stormont's agriculture department is to be investigated by the UK-wide environmental protection agency over its guidance to farmers and planners on controlling harmful emissions.
The statutory probe follows complaints from a member of the public about the Department of Agriculture, Environment and Rural Affairs' so-called Operational Protocol, which offered advice on planning applications for livestock housing.
The investigation will assess whether the department's Standing Advice on Livestock Installations and Ammonia, which was issued in 2017 when no minister was in post, failed to comply with environmental law.
Northern Ireland's agriculture sector is responsible for more than 90 per cent of the region's ammonia emissions, which have a damaging impact on sensitive habitats and biodiversity, as well as human health.
Planners are responsible for carrying out assessments to ensure all applications meet habitats regulations.
The Office of Environmental Protection (OEP) is the body's first investigation since its powers were extended to the north last year.
The agency's head Natalie Prosser said ammonia emissions had increased by 19 per cent "from an already unsustainable level" in the decade to 2019.
“Unsatisfactory ammonia pollution is an important, longstanding, systemic issue and one of the most pressing environmental concerns at this time in Northern Ireland," she said.
Ms Prosser said the OEP probe would provide "clarity on environmental impacts when planning decisions are being made".
If Daera is found to have failed to comply with environmental law, the OEP will aim to resolve the matter through "co-operation, dialogue and agreement with public departments and authorities".
However, where a satisfactory outcome cannot be reached through these means, stricter enforcement powers can be used.
The department has been contacted.
