Northern Ireland's First Minister Arlene Foster said the Northern Ireland Protocol has been "absolutely devastating" for the region.
She said she welcomed "small moves" by the UK government and accused the EU of "hysteria" in reaction to the extension of some grace periods, with threats of legal action.
"I think this is something that really does need to be concentrated on to get a replacement for the Protocol," she told LBC Radio's Swarbrick on Sunday show.
"The European Union are very focused on protecting their single market, which is the European single market, but they don't mind at all if it's damaging the internal market of the UK.
"I welcome the fact that government did move but there's much more to do, and actually the architecture of the Protocol itself needs to be dealt with."
Ms Foster has called for alternatives to the Northern Ireland Protocol to be considered.
"There are other alternatives, of course those alternatives were rejected by the European Union, whether it was alternative arrangements, whether it was their own smart borders or indeed mutual enforcement which, of course, could be put in place as well," she said.
"In order to find a solution, you have to have people who are willing to look for a solution, and up until now when we have indicated that the entire unionist community in Northern Ireland want this Protocol gone, the answer you get from the European Union is 'yes, we should have more Protocol'. It's crazy, absolutely crazy."
EU Commissioner Mairead McGuinness has said things are particularly difficult and the Commission was "a bit surprised to say the least" that the UK took its own decision to extend dates.
Speaking about ongoing issues with the Northern Protocol on RTÉ's The Week in Politics, she said practical problems have to be solved but the UK also has to acknowledge the situation is because of Brexit and the form of Breixt the British Prime Minister Boris Johnson wanted and forced through.
She said the Commission understands communities in Northern Ireland are disaffected and upset but it was their Prime Minister who agreed to this protocol and who is duty bound to implement it.
Asked if she thought Mr Johnson would be deterred by a European Court of Justice ruling, she said she was not sure she understood Mr Johnson's mind, but the Commission is duty bound on behalf of members to make sure an international agreement is complied with and there may be some developments this week on some of the legal aspects.
She said the Commission will do what it need to do.
It has been a poor week for relations, and the move by the UK showed no sense of diplomacy and was really not a very good step, she added.
She said there have been difficult moments with the UK in the past which continues to seem to negotiate with itself how great Brexit is, almost as if trying to convince themselves.
Sinn Féin Leader Mary Lou McDonald defended the Northern Ireland Protocol and said it seems those who voted for Brexit are not willing to face up to the consequences of it.
She said the protocol brings necessary protections.
It comes as the UK's chief Brexit negotiator David Frost called on the European Union to "shake off any remaining ill will" towards the UK for leaving the EU as arrangements governing trade to Northern Ireland continue to prove contentious.
The European Commission has said it will begin legal proceedings after London announced it was extending a series of "grace periods" designed to ease trade between Northern Ireland - which remains in the EU single market for goods - and Great Britain while permanent arrangements are decided.
Mr Frost said on Wednesday that Britain's move should allow time for constructive discussions with counterparts in Brussels.
But the intervention provoked a furious response in Brussels, with the EU accusing the UK of going back on its treaty obligations in the Brexit Withdrawal Agreement intended to ensure there is no return of a hard border between Northern Ireland and Ireland.
Writing in The Sunday Telegraph, he said the move is lawful and designed to protect the everyday lives of people in Northern Ireland.
He said: "With Boris Johnson as Prime Minister, our agenda is one of an outward-looking country, confident we can work with others towards common goals.
"That is our hope for our ties with our European friends and allies too. I hope they will shake off any remaining ill will towards us for leaving, and instead build a friendly relationship, between sovereign equals."
The Northern Ireland Protocol in the Withdrawal Agreement was designed by the EU and UK to avoid a hardening of the border on the island of Ireland.
It means keeping Northern Ireland aligned to various EU rules, requiring checks on goods arriving from Great Britain.