Nigel Dodds has said the DUP believes Prime Minister Theresa May is the right person to lead the United Kingdom into Brexit.
He was speaking on the “historic day” when Article 50 was triggered, beginning the formal process of the UK leaving the European Union.
"The Prime Minister has rightly been emphasising her determination to deliver for all constituent parts of the United Kingdom on this historic day,” said Mr Dodds, during Prime Minister’s Questions.
"And whilst others are content to moan and whine we want to see that delivery happen and we are confident she will make that happen."
Meanwhile Sinn Féin MEPs have been taking part in an anti-Brexit protest at Stormont.
The party’s northern leader Michelle O’Neill said the campaign to secure special designated status for Northern Ireland is building momentum.
"Brexit would be a disaster for Ireland, socially, politically and economically," she said.
"It is unacceptable that Tories, who have no mandate in Ireland, can impose Brexit and a border against our will. The people of the north voted against Brexit in a democratic poll."
The Ulster Unionist Party also campaigned for ‘remain’ but, since the result, have voiced support for the referendum result to be actioned.
UUP MP Danny Kinahan told the Commons: "May I congratulate the Prime Minister and the Government on today triggering Article 50.
"I know this a momentous action for the whole of the United Kingdom.
"And while I, like herself, campaigned to stay in, we recognise that the people have spoken and we offer, the UUP, full support in ensuring that negotiations deliver the best for the whole of the United Kingdom and particularly for Northern Ireland."
Meanwhile the SDLP leader Colum Eastwood, who took part in the demonstration at Stormont, said triggering Article 50 when Northern Ireland had no powersharing executive in place was an act of "democratic savagery".
He added: "The British government's Brexit juggernaut is about to smash through the fragile complexities of Irish politics".