He said: “For well over a year now, we have been making the case to parties in the South, in Britain and across Europe that the only way to defend Northern Ireland’s economic interests is to remain in the Customs Union and Single Market.
“Free movement of people, goods and services across this island is the key context to our political dispensation, it should not be torn up in a bid to satisfy extreme brexiteers.
“I welcome Jeremy Corbyn’s announcement this morning, it is the first step in the right direction by the Labour leadership.
“I met the Labour Leader last week in London to discuss this very issue and made the case very strongly to him that Labour should build on its peace process legacy by ensuring that the layered complexities of our political settlement are preserved, not destroyed.
“The clear and positive change in policy from our sister party is a welcome development.
“The Labour Leader must continue to take a stand against Theresa May and her drift toward a hard Brexit/hard border result in Ireland.
“There is still a long way to travel to protect the North’s interests.
“There is a clear and concerted campaign by individuals in Britain to undermine the Good Friday Agreement in the pursuit of an aggressive Brexit that will bring back a hard border. Those individuals must be called out by their parties.
“Alignment with the rules of the Single Market, as outlined in the phase one agreement, is critical to protecting Northern Ireland from the economically irrational ideology of the brexiteers. It is to this position Jeremy Corbyn must now have the courage to carry his party.
“The SDLP will continue to work with parties across these islands and across this continent to protect our people from Brexit.”