Boris Johnson hailed the signing of the Northern Ireland protocol and withdrawal agreement as a "fantastic moment" for the UK in January last year, but now says it is not working and that it must be changed.
Speaking in the House of Lords on Monday evening, David Frost, the government's Brexit minister, said the EU should come to the table to make changes to the accord.
"They would be making a significant mistake if they thought that we were not ready to use Article 16 safeguards, if that were to be the only apparent way forward to deal with the situation in front of us," he told peers
"If we are to avoid this situation, there needs to be a real negotiation between us and the EU."
Lord Frost, who negotiated the agreement as a special advisor with wide ranging executive powers but who has since been appointed to the legislature and made a government minister, added: "A real negotiation does not mean the EU coming up with its own plans for solutions, within the framework of the existing Protocal, and presenting them to us as 'take it or leave it'."
Britain says it wants "substantial and significant change" to the agreement, which is causing disruption to internal trade between Great Britain and Northern Ireland as predicted by critics when it was originally proposed by the government.
The UK has already extended post-Brexit grace periods on imports and exports to try and soften any effects - last week saying it would do so again.
Under Article 16 the protocol, which governs trade relations between the two territories, would effectively be set aside.
The article allows one or both sides to suspend the deal if it is found to be causing "serious" problems, but does not give a firm definition of what counts as "serious".
The agreement negotiated by Lord Frost and Boris Johnson keeps Northern Ireland in the EU single market and customs territory, while the UK sits outside of it.
As well as causing frictions, the deal has some advantages for Northern Ireland, which can trade more freely with the the EU than Great Britain.
It also eliminates a hard border with the Republic of Ireland, which was the original intent of the protocol. Both these aspects would be lost if the deal was suspended, though there is significant uncertainty over the enforcement of a hard border in the absence of an agreement.
The EU's Brexit chief Maros Sefcovic, has flat-out rejected the idea of renegotiating the deal. Officials in Brussels say members states have no appetite whatsoever for negotiating with Britain after having signed a deal so recently
Lord Frost told peers: "I don't in fact take Commissioner Sefcovic's words as a dismissal of our position, I take them as acknowledgement of it.
"But I also take it as a fairly clear indication that there is more to be done. So I do urge the EU to think again."