Mike Nesbitt has pledged to place libel reform in the negotiations for a Programme for Government in the next Assembly.
The Ulster Unionist leader said it was time to sort out our decades-old legislation.
Although the law on defamation was updated in England and Wales in 2013, Stormont stopped the changes coming in here.
It has prompted warnings that our unreformed system poses a threat to freedom of speech.
Mr Nesbitt said: "I will bring the issue of libel reform to the negotiations on the next Programme for Government and if there is no commitment to address it there, I will bring forward another Private Member's Bill in the next Assembly mandate to sort it out."
A previous Private Member's Bill by Mr Nesbitt was blocked in the last Assembly.
He referred the matter to the Northern Ireland Law Commission for consultation. It will make recommendations in the next Assembly session.
But campaigners warn that without cross-party political support these proposals could be sidelined by a minority of MLAs.
Campaigners have mobilised hundreds of people across Northern Ireland to urge libel reform.
They are backed by writers, academics and scientists.
Sile Lane, campaigns director of Sense About Science, said change was long overdue.
"Thousands of citizens in Northern Ireland back the campaign and there is overwhelming public support for libel law reform," she said.
"They want doctors to be able to discuss evidence for treatments, consumer magazines to be able to review products and journalists to investigate local issues without fear of being dragged into court if someone doesn't like what they say."
Concerns over lack of protection for free speech in Northern Ireland have risen in recent times.
Last year Sky Atlantic temporarily pulled a broadcast of Going Clear, an acclaimed Hollywood film about Scientology, across the whole of the UK over fears it could be liable for damages at the High Court in Belfast.