Hundreds of people are attending a rally in Belfast calling for a second referendum on EU membership.
Campaigners from the People's Vote rally say the public deserves to make the decision over whether the British Government's Brexit deal is the right choice.
Speakers at the rally in Belfast include Dominic Grieve QC MP, the SDLP's Claire Hanna, Green Party NI leader Clare Bailey and MEP Naomi Long.
The event is being compered by Alastair Campbell.
Leader of the Alliance Party Ms Long told the huge crowd that gathered in Belfast's Ulster Hall that the Good Friday Agreement is under threat from Brexit.
"We all know in Northern Ireland that while Brexit is challenging for everyone, for the EU, it is an existential challenge here in Northern Ireland and a no-deal would be catastrophic," she said.
"We have to avoid that at all costs. Brexit was never a good idea.
"At a time when the main challenges that face us are global challenges, whether it's climate, security, peace, tax transparency, our lives are more connected than ever before.
"It makes no sense to withdraw from a large international influential block."
Ms Long added: "People were promised a unicorn Brexit that doesn't exist, a fantasy Brexit that we could trade with everyone without tariffs while protecting all our jobs and skills and making so much money.
"At the same time we were told we would continue to trade normally with the European Union.
"That Brexit does not exist. This Prime Minister can't even deliver a donkey of a deal.
"Let's get the facts out there that we will be worse off as a nation."
Ms Bailey said that Northern Ireland stands to lose the most in Brexit.
She added: "I view the referendum as a bad call and an in-house fight. It was never intended to be in the interest of the people.
"I don't see it as the will of the people. We have 52% of people who voted to leave based on a campaign found to have broken electoral law and told lies and misinformed people.
"I don't see that as democratic."
Ms Hanna said: "The message we have to send from here is we want our stability and future back.
"This is about protecting the welfare of everyone here, including those who voted to leave.
"We need to say to those who voted to leave that we understand your concerns.
"We can end austerity or we can end Brexit but we certainly cannot do both.
"The most plausible way out of this quagmire is a second vote."