Problems with the Northern Ireland Protocol need to be flushed out “pretty fast”, the Prime Minister has said.
Boris Johnson also said the way the post-Brexit agreement is being interpreted is “not coherent” with the principles of the 1998 Good Friday Agreement.
Mr Johnson was speaking following a visit to an integrated school in Co Antrim.
The EU and UK are set for an intense round of negotiations in the coming weeks after European Commission vice president Maros Sefcovic last week unveiled a range of proposals aimed at cutting the red tape the protocol has imposed on moving goods from Great Britain to Northern Ireland.
However, the plan did not address a key UK demand – the removal of the oversight function of the European Court of Justice (ECJ) in the operation of the protocol.
Speaking to the media, Mr Johnson said: “I think there is an issue with the protocol and we need to thrash that out.
“We can’t go on forever with this question because it is affecting real people and real lives and real businesses right now because of the way in which the protocol is being interpreted.”
He added: “I don’t think that it is coherent with the Belfast/Good Friday Agreement because the way it is being used is creating these unnecessary checks down the Irish Sea.
“So we need to flush it out pretty fast and we need to change the causes of the problem and not the symptoms and I think we need to move pretty fast.”
The Northern Ireland Protocol was agreed by the UK and EU as a way to sidestep the major obstacle in the Brexit divorce talks – the Irish land border.
It achieved that by shifting regulatory and customs checks and processes to the Irish Sea.
But the arrangements have created new economic barriers on goods moving from Great Britain to Northern Ireland.
This has caused disruption to many businesses in Northern Ireland and has also created a major political headache for the Government, as unionists and loyalists are furious at what they perceive as a weakening of the Union.