Brexit Minister Lord Frost has blamed negotiators under Theresa May as being responsible to a "very large degree" for issues with the Northern Ireland Protocol.
The Conservative peer was grilled in person by assembly members on Stormont's Executive Office Committee, which is scrutinising issues arising from Brexit, on Friday.
Lord Frost argued that the problems with the post-Brexit agreement that has caused a trade barrier in the Irish Sea are largely down to the EU's implementation of the deal he helped broker.
But he argued that the Protocol could have been better negotiated if it were not for the work done by the team of Boris Johnson's predecessor as prime minister.
DUP member Christopher Stalford quoted Mrs May's former chief of staff, Lord Barwell, who has claimed the Mr Johnson's Government "knew it was a bad deal" but intended to "wriggle out of it later".
Mr Stalford said that Lord Frost had inherited "a dog's breakfast of a deal, adding: "You've been left to clean up the mess haven't you?"
Lord Frost responded: "We intend to implement what we signed up to, but it's the fact of implementation that's causing the problem.
"I would say that it was the inheritance that we inherited from the previous Government and from the previous negotiating team that has been a significant part of the difficulty and the reason the Protocol is shaped as it is is because we had a particular inheritance from the previous team who could not get their deal, rightly in my view, through Parliament.
"Unfortunately, we were not able to go back to scratch and do things in a different way and I think the previous team are to a very large degree responsible for some of the infelicities in this Protocol and the Withdrawal Agreement that we might be better without but unfortunately we are where we are."
Lord Frost argued that it is unreasonable to describe the Protocol as a "definitive text" with no further discussions around it required.
"I don't think it's right to look at the Protocol as a sort of definitive text that was there in October 2019 and there's nothing more to say. It's very clear from reading the text that that's not the case," he said.
"For example, the whole concept of goods at risk, which is obviously at the core of some of the problems in movements between GB and Northern Ireland.
"It's not reasonable to say, given that the situation has changed in various ways and given that parts of the Protocol remained to be worked out, that it is a definitive text and, as of October 2019, that's it and there's nothing more to say."
Meanwhile, Sir Jeffrey Donaldson has spoken with Prime Minister Boris Johnson for the first time since becoming DUP leader and the NI Protocol was high on the agenda.
The pair spoke over the telephone on Friday afternoon.
Speaking afterwards, Sir Jeffrey said: "I took the opportunity to remind him (Boris Johnson) that my number one objective is to restore our place within the UK internal market.
"The Northern Ireland Protocol has damaged the economic and constitutional integrity of the Union. We will work with the Prime Minister and others in Parliament to deal with the Protocol. It is flawed and cannot remain.
"We also discussed the need for Northern Ireland to benefit from the Government's 'levelling up' agenda and in particular for enhanced connectivity between Northern Ireland the rest of the United Kingdom."