The new Westminster leader of the DUP, Sir Jeffrey Donaldson, has pleaded with Boris Johnson to address the Northern Ireland customs arrangements in his Brexit deal.
The DUP's leader in the House of Commons was speaking as the Tory government began its attempt to push Brexit legislation through Parliament.
Mr Donaldson said: "We supported Brexit, and we want Brexit to happen and we acknowledge and recognise that the Government has won a mandate to take forward its Withdrawal Agreement.
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"But there is a major contradiction at the heart of that agreement which causes us great concern. At the one level the agreement does say that Northern Ireland should continue to have unfettered access to the rest of the UK for trade, but then we have customs arrangements that inhibit our ability to have that unfettered access, and that is our major concern, and one that we hope the Government can address."
Mr Donaldson added: "I want the prime minister to treat my part of the United Kingdom the same as the other parts in the context of leaving the European Union."
Mr Donaldson said that while he welcomes the fact that the assembly will have a say over special arrangements, he believes the arrangements "will continue unless the assembly stops them" which requires a vote in the Assembly - and that there are "issues around how that would be exercised".
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He added: "We do want the assembly to have a say, but we want to ensure that say can be exercised in a fair manner that respects the principle of consent as set out in the Belfast Agreement."
The DUP's Gavin Robinson said Mr Johnson "needs to understand the concerns about customs arrangements for Northern Ireland".
He added: "We're not going to resolve those issues today, but will the prime minister commit to proper and thorough and detailed reconsideration using the strength he has, to deliver for the entirety of this country?"
Mr Johnson replied: "Let me remind him that the deal commits to unfettered access, unfettered access in all parts of the UK, respects the territorial integrity of the UK and ensures that Northern Ireland is part of the UK customs territory and will therefore benefit immediately from any of our new free trade deals as soon as they are in force."
Labour leader Jeremy Corbyn said Mr Johnson's claims that there will be no checks between Northern Ireland and Great Britain are "simply not true."
Mr Corbyn added that checks and customs declarations in the Irish Sea will have "a huge impact on Northern Ireland businesses and society" and will also have "implications for the rest of Britain's economy and manufacturing industry".
He continued: "If we believe the government is taking the wrong approach, we should never be afraid to oppose. And when it comes to our future relationship with the European Union and the rest of the world, we cannot let this Government act in an undemocratic and secretive way.
"Trade deals with the EU and the United States, and anybody else for that matter, must be done transparently."
He concluded: "As we leave a 40-year economic partnership for an unknown future under the terms of the withdrawal deal we need, Mr Speaker, an approach that puts jobs and living standards first and builds the strongest co-operation with our European neighbours based on openness, solidarity and internationalism.
"And that, Mr Speaker, is the approach that will bring an end to the Brexit crisis and bring our country together."
