The Prime Minister often talks about his Brexit deal being “oven-ready” – but could what he’s planning to cook up leave a bitter taste for those in Northern Ireland?

Jeremy Corbyn and Labour certainly think so, after publishing internal Treasury analysis about what the Withdrawal Agreement could mean in terms of checks on goods being traded into the six counties from Great Britain.

Boris Johnson denies there is any truth in the report, that Mr Corbyn called “damning”.

Here is a look at what has been said, both now and in the past, about the withdrawal deal’s impact on Northern Ireland.

– What is this document Labour has got hold of?

Jeremy Corbyn
Jeremy Corbyn holds up a leaked document relating to Northern Ireland (Jonathan Brady/PA)

As with many Whitehall documents, the boring name – NI Protocol: Unfettered Access To The UKIM (Internal Market) – disguises the significance of its 15-pages of contents.

Brandishing the analysis at a central London press conference on Friday, Mr Corbyn said the documents were “cold hard evidence” that Mr Johnson had been “misrepresenting” his exit terms as good for the whole of the UK.

The Labour leader said page five of the document stated: “There will be customs declarations and security checks between Northern Ireland and Great Britain.

“For trade going the other way, from Great Britain to Northern Ireland, there will be all of the above plus potentially damaging tariffs.”

The possibility of customs declarations being required had been suggested previously by ministers – but for tariffs to be slapped on some goods was an entirely new proposition.

If true, these new arrangements would have financial repercussions for businesses on both sides of the Irish Sea.

– Is the Prime Minister conceding defeat on this?

Not at all – in fact, he has gone so far as to call the report’s contents “complete nonsense”, despite not having read it.

“I haven’t seen the document you’re referring to, but that’s complete nonsense, and what I can tell you is that with the deal that we have, we can come out as one whole UK,” he told reporters on the campaign trail on Friday.

– Has this always been Mr Johnson’s stance?

Boris Johnson
Boris Johnson in Kent on the campaign trail (Stefan Rousseau/PA)

The Conservative leader has been firm on this throughout the election campaign.

During a visit to Northern Ireland in November, at the very start of his UK election tour, he told businesses they could put customs declaration forms “in the bin” because there would be “no barriers of any kind” to trade crossing the Irish Sea.

But Mr Johnson told the BBC in October, after agreeing his deal with the European Union, that there would be checks on some British goods in order to avoid a hard border in Ireland.

“What we have agreed with the EU is that temporarily, and by consent of the people of Northern Ireland, if there is stuff coming from GB into Ireland, or anywhere else in the world via Northern Ireland into Ireland then, yes, there can be checks,” he said.

– And what about others in Government – do they think there could be checks?

Stephen Barclay
Brexit Secretary Stephen Barclay told MPs some checks on goods travelling between Northern Ireland could be necessary (Jonathan Brady/PA)

Brexit Secretary Stephen Barclay, who was heavily involved in the negotiations, told MPs that customs “interventions” could be incoming after exit day.

Speaking in the Commons in October, he said that “some information” and “minimal targeted interventions” would be required on goods travelling between the two parts of the UK, due to Northern Ireland remaining aligned with Dublin and Brussels’ trading rules for agricultural products and manufactured items.

– So who is right on the customs and border issue?

Politics is rarely without “grey areas” and the mechanics of the Northern Ireland-Great Britain trading relationship after Brexit appears to be one of those areas.

Page 293 of the Withdrawal Agreement notes that “nothing in this protocol prevents the United Kingdom from ensuring unfettered market access for goods moving from Northern Ireland to the rest of the United Kingdom’s internal market”.

But if it were that simple, why have Mr Barclay and the Treasury got themselves so muddled over whether customs declarations and even tariffs might need to be applied?

The answer to that is unclear. But what is plain is that Mr Johnson’s main course on Northern Ireland has yet to win any five-star reviews.