The Assembly has been urged to commit Northern Ireland to annual cuts in greenhouse gas emissions.
The Executive has not yet promised to make cuts in carbon dioxide emissions, despite backing plans for a UK-wide law to tackle climate change, according to green leader Tony Juniper.
The Friends of the Earth director will call on the Assembly to play its part in battling climate change when he attends a public meeting in Belfast this evening.
He will also tell business leaders, civic leaders and activists that urgent action on climate change is crucial, and that many of the solutions already exist.
Through 'The Big Ask' climate campaign, Friends of the Earth has campaigned for Parliament to introduce a new law to cut UK carbon dioxide emissions. Labour has agreed to legislate and is due to introduce a Climate Change Bill next month.
Although welcoming the move, Friends of the Earth says that the proposals must be tougher to be effective.
Mr Juniper said: "I am delighted that the Northern Ireland Executive has given its backing to a new UK law to tackle climate change. But Stormont politicians should go further and commit Northern Ireland to annual cuts in its emissions too.
"The region could play a significant role in helping the UK become a world leader in developing a low-carbon economy."
He will also urge Northern Ireland politicians to call on the Government to strengthen its proposals for a new climate law.
"I hope that Northern Ireland Executive members will urge the UK Government to strengthen its plans for a new climate law. It should commit the UK to cuts in carbon dioxide emissions of at least 3% each year, and include Britain's share of pollution from aviation and shipping."
Tony Juniper will be speaking at The Black Box, Hill Street, in the Cathedral Quarter at 8pm.