Post-Brexit trading arrangements were always meant to be flexible, a minister has argued, as he suggested the EU could yet back down and renegotiate the Northern Ireland Protocol.

Brexit minister Lord Frost said on Wednesday that the Northern Ireland Protocol, part of the Brexit divorce deal agreed by the UK and Brussels, was undermining the Good Friday Agreement and urged the European Union to look at UK proposals for change.

The EU has said it will not reopen negotiations but suggested there could be room for manoeuvre within the existing agreement.

However, Business Secretary Kwasi Kwarteng said the protocol, which effectively keeps Northern Ireland in the EU’s single market for goods, was never “something that was going to last forever”.

He told Sky News: “A deal is a deal but it wasn’t something that was going to last forever.

“Nobody thought the Northern Ireland Protocol was going to define the role of Northern Ireland within the UK forevermore, it was something that was flexible.

“You’ll remember two years ago people said we were never going to get a deal from the EU but we did so.

“When people say they’re not going to look at the protocol again, I say ‘well, let’s just see’.”

The protocol was put in place to ensure there would be no hard border with Ireland, but it has instead effectively placed a trade barrier in the Irish Sea.

However, Lord Frost said the economic and social damage caused by the arrangements would have justified the use of Article 16, effectively tearing up parts of the deal.

The difficulties caused by the arrangements have meant Northern Ireland had faced reductions in supermarket product lines.

Marks & Spencer’s chairman warned there will be some “gaps on shelves” in Northern Ireland this Christmas.

One idea put forward would be for UK traders to declare whether the final destination for their goods was Northern Ireland or the Republic.

European Commission vice-president Maros Sefcovic flatly rejected the UK’s call to renegotiate elements of the agreement on Wednesday.

Lord Frost’s proposals are thought to require changes to at least three of the protocol’s articles.

He called for a “standstill” period, preserving the current grace periods and suspending legal action taken by the EU against the UK while changes are negotiated.