Steve Baker has apologised to the European Union for "not always behaving" during Brexit negotiations.
The new Northern Ireland minister was a staunch supporter of the Leave campaign and is a former chairman of the European Research Group, made up of backbench Conservative MPs.
He was one of 28 "Spartan" Tories who voted against Theresa May's Brexit deal on all three occasions, and resigned as Brexit minister in 2018 over his fears she had accepted compromises that effectively kept Britain in the EU.
However, he struck a more conciliatory tone in the main hall of the Conservative Party conference on Sunday, saying that relations between Britain and Ireland were not "where they should be".
Repairing relations with Brussels and Dublin
Mr Baker said: "The thing I want to add, as one of the people who perhaps acted with the most ferocious determination to get the UK out of the EU: I think we have to bring some humility to this situation.
"It is with humility that I want to accept and acknowledge that I and others did not always behave in a way which encouraged Ireland and the European Union to trust us, to accept that they have legitimate interests, legitimate interests that we are willing to respect.
"Because they do and we are willing to respect them, and I am sorry about that, because relations with Ireland are not where they should be and we all need to work extremely hard to improve that and I know that we are doing so."
Britain's relations with both Brussels and Dublin have soured further over the Northern Ireland Protocol, which Liz Truss's government has blamed for trade friction.ave soured further over the Northern Ireland Protocol, which Liz Truss's Government has blamed for trade friction.
The Prime Minister brought forward legislation when she was foreign secretary to allow the unilateral suspension of parts of the Protocol, but has insisted her preference would still be a deal with the European Union to remove the most problematic aspects of the agreement.
Chris Heaton-Harris, the Northern Ireland Secretary, said he had "learnt a lot in the last few years about the delicate political and trade impasse".
He also appeared to row back from the hard line on Brussels that defined Boris Johnson's premiership, adding: "I understand the complications. Maybe we could have understood them a bit better sooner."
'EU not enormously keen on the UK'
However, Jacob Rees-Mogg, the Business Secretary, took a harder line, saying that the EU was "not enormously keen on the United Kingdom" and is stopping the Brexit trade deal from working "fluidly".
"We cannot allow the European Union to stop us trading with Northern Ireland from Great Britain," he told a fringe event held by Conservative Home.
"It's monstrous and the legislation is with parliament to deal with that. It's about to arrive in their Lordships' house and I hope their Lordships will give it fair passage."