Northern Ireland must do more to cut its greenhouse gas emissions, its environment minister said after figures showed it falling behind the rest of Britain.

Statistics from the British Department of Environment Food and Rural Affairs released Friday indicated Ulster had reduced its greenhouse gas emissions by 5 percent in 2011 over the previous year, to 1.98 million tons of carbon dioxide equivalent.

Meanwhile, the 2011 levels also continued a longer-term decrease of more than 17 percent since the 1990 base year.

But while that was good news on an absolute level, Northern Ireland Environment Minister Alex Attwood said, the numbers also showed the country is lagging behind the rate of emissions reductions happening in the rest of Britain.

The nation as a whole has cut its greenhouse gas emissions 29.1 percent over the base levels, while England (30.9 percent), Scotland (30.8) and Wales (20.6 percent) have all outpaced Northern Ireland's 17.5 percent reduction.

Attwood said much more must be done if Ulster is to meet air pollution goals.

"It is clear to me that we need to redouble our efforts to reduce our emissions even further so that we can meet the [government] target of a 35 percent reduction by 2025," he said. "All of us, including ministers, government departments and broader civil society, have responsibility for this."

The 5 percent drop in Northern Ireland's emissions for 2011 was chalked up to a large reduction in the use of burning oil in the residential and business sectors following an exceptionally cold winter in 2010.

Northern Ireland, unlike the other parts of Britain, sees the largest sources of carbon emissions coming from agriculture -- a total of 28 percent. While other types of greenhouse gas sources, such as emissions from power plants, can be cut by converting away from the burning of fossil fuels, agricultural sources are much harder to reduce with simple measures.

Agricultural activities that release greenhouse gases can range from fertilizer application to methods of irrigation and tillage, while livestock, especially cattle, produce methane as part of their digestion.

The government this month launched a consultation on a proposed Northern Ireland climate change bill, which, if enacted, would change the current voluntary efforts by country's agriculture sector into mandatory ones.

"I believe experience has shown that specific regional climate change legislation plays a part in delivering real sustainable change and I firmly believe that is the way we should go," Attwood said.

The Ulster Farmers Union, however, has warned such an approach could "crush" Northern Ireland's $6.2 billion farm economy.

"We are disappointed that the environment minister's pre-consultation on the proposed climate change bill did not acknowledge the significant opportunities the agri-food sector can deliver for our economy," the UFU said in a statement issued Saturday.

UFU Deputy President Ian Marshall told members of a climate change bill stakeholders panel last month in Belfast an upcoming report from Northern Ireland's Agri-Food & Biosciences Institute was expected to show the only way in which climate change legislation could reduce emissions in agriculture is through the introduction of climate change levies.

That, in turn, could trigger a "significant reduction in food output and a decline in exports," as well as have a detrimental impact on the physical environment in rural areas, he said.