SDLP Leader Colum Eastwood said Brexit is “the most dangerous economic, social and constitutional crisis to face this island since partition”.
He was speaking after the British Government published the European Union (Withdrawal) Bill, known as the Repeal Bill.
Mr Eastwood said: “The North of Ireland is cut out of formal talks with the head negotiator Michel Barnier due to the absence of a government here.
“While Scotland and Wales meet with the EU lead, we are left without a voice at that table.
“In Westminster, Irish nationalism is silenced as Sinn Fein MPs refuse to take their seat to fight the destructive Repeal Bill.
“I’ve said it before and I’ll say it again, Brexit is the most dangerous economic, social and constitutional crisis to face this island since partition. It demands our immediate attention and our immediate response.
“The issues facing the restoration of our institutions are not insurmountable. It is up to the DUP and Sinn Fein now to get that deal done.
“The summer cannot be wasted.
“We must return a system of sustainable devolution.
“The alternative is that we are dragged into direct rule, where the pro-Brexit Tories and DUP have a free hand on our futures.
“Those of us elected on mandates to fight a hard Brexit, must be able to do that.
“The threat posed to this part of our island cannot be underestimated, we must restore the institutions to resist it.
“Only by preventing legislative consent in the institutions will we be able to put a spanner in the works for the British Government in relation to the Repeal Bill.
“We cannot be left behind, it is our responsibility to prevent this catastrophe,” added the Foyle MLA.
