Mike Nesbitt has said reform of the north's libel laws will be part of post-election programme for government negotiations.
The Ulster Unionist leader's private member's bill that would have brought defamation laws into line with Britain was blocked when finance minister Simon Hamilton referred the issue to the Northern Ireland Law Commission for consultation.
Westminster updated its libel laws in 2013 but Mr Hamilton's predecessor Sammy Wilson chose not to introduce the reforms to the assembly.
The move has created the potential for 'libel tourism', where people who believe they have been defamed seek to have the cases heard in Northern Ireland where the law differs.
Last year Sky Atlantic temporarily pulled broadcast of Going Clear, an acclaimed Hollywood film about Scientology, across the entire UK over fears it could be subject to libel action at the High Court in Belfast.
"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," Mr Nesbitt said.
His pledge came as a group of lawyers, academics and writers calling for libel reform urged assembly election candidates to back their campaign.
They said the overdue report by the Northern Ireland Law Commission would make recommendations in the next session of the assembly, but without political support could end up sidelined.
A spokesman said a consultation campaigners had carried out showed 95 per cent of respondents supported reform of the law, elements of which pre-date the invention of the light bulb.
Like Mr Nesbitt, the SDLP and Alliance support a change in the legislation.
A Sinn Féin spokesman said it had not made a policy decision but was broadly supportive of libel reform and recognised the need to review "out-of-date" defamation laws, especially to reflect technological changes.
A DUP spokesman said: "It should be noted that different regions of the United Kingdom have not all adopted the same position in terms of libel reform.
"An independent study is currently being completed assessing whether change in this area is required. We want to see that independent legal view before deciding to take forward any particular approach."
