Alliance Brexit spokesperson Stephen Farry MLA has said if the Brexit process has not reached a "positive and constructive conclusion" by April 12, the UK Government has no other option but to revoke Article 50.
Dr Farry was speaking after MPs voted to reject Theresa May's proposed Withdrawal Agreement by 344 votes to 286. It means the Prime Minister now has until April 12 to seek a further extension to avoid a no deal Brexit.
"The UK Government and Parliament have together deepened an already major crisis. The future economic prosperity and cohesion of the UK is at stake," he said.
"A no deal Brexit would be a disaster for the UK as a whole but a catastrophe for Northern Ireland. It must be avoided at all costs. Every day this crisis continues, untold damage is happening to our economy, people's jobs and livelihoods, plus our international reputation.
"For Alliance, the current Withdrawal Agreement, including the backstop, was always the absolute minimum acceptable. And there can be no retreat on the backstop. But we have always preferred different approaches, including a People's Vote to reconsider Brexit or a soft Brexit UK-wide.
"If the current version of the Withdrawal Agreement is no longer viable, then the choices for the Government and Parliament are narrowed to amending the Political Declaration to indicate a Customs Union and remaining in the Single Market, or putting the Withdrawal Agreement to a referendum. Indeed, it may well be both of those approaches should be combined.