Supermarkets will be given a “grace period” to ensure food supplies from GB to NI do not face disruption from 1 January, the government has said.
This will give supermarkets time to adapt their systems to deal with new Brexit checks required by the EU.
It is part of the agreement reached between the UK and EU on how the new Irish Sea border will operate.
The rules will apply regardless of whether the two sides can agree a trade deal.
Later on Wednesday, Prime Minister Boris Johnson will travel to Brussels for talks on a post-Brexit deal with the European Commission President Ursula von der Leyen.
‘British sausages for Belfast’
Cabinet Office Minister Michael Gove outlined further details of the agreement reached with the EU on how the NI part of the original withdrawal deal, known as the Protocol, will work.
He said the government had heard “loud and clear” the concerns of supermarket firms and that “necessary additional flexibilities” would be made.
The so-called grace period will initially be for three months, with six months guaranteed for chilled meat products, he said.
From 1 January, Northern Ireland will stay in the EU single market for goods but the rest of the UK will leave.
That means a proportion of food products arriving in Northern Ireland from Great Britain will need to be checked.
The EU has strict rules on products of animal origin: meat, milk, fish and eggs.
These products must enter through a border control post where paperwork is checked and a proportion of goods are physically inspected.
Several supermarket chains had warned the supply of some products from GB to NI could be reduced, due to extra administrative burdens.
On Wednesday, Britain’s biggest supermarket Tesco said it was stockpiling food ahead of a potential no-deal Brexit.
Mr Gove said the agreement “also prevents any disruption at the end of the transition period on the movements of chilled meats”.
“British sausages will continue to make their way to Belfast and Ballymena in the new year,” he added.
But Sir Jeffrey Donaldson, the Democratic Unionist Party (DUP) Westminster leader, said “safeguarding the union is not a three-month project” – but an enduring commitment.
He asked Mr Gove to commit, if necessary, to introducing ongoing “safeguard measures” to maintain unfettered access between Northern Ireland and Great Britain.
The DUP had opposed the protocol in Parliament, arguing it would create a divide between NI and the rest of the UK that threatened to break up the union.
The supply of medicines from GB to Northern Ireland will also avoid disruption, with the industry granted a period of 12 months to adapt to the changes under the Protocol.
Mr Gove said the government had delivered on its commitment to ensure unfettered access for NI firms shipping goods to the rest of the UK.
“No additional requirements will be placed on NI businesses for these movements, with the very limited and specific exception of trade in endangered species and conflict diamonds,” he said.
The UK and EU have also agreed a trusted trader scheme, which means most goods going from Great Britain to Northern Ireland will not face any tariffs.
The Northern Ireland Protocol created a category of “at risk goods”.
These are goods which the EU fear could travel from GB through NI into the Republic of Ireland and the wider EU, without paying the correct EU tariff.
The protocol makes a provision for tariffs to be charged on these goods.
It was feared that a large proportion of goods going from GB-NI could have attracted tariffs in this way.
But a UK official has told the BBC a new trusted trader scheme, agreed with the EU, would exempt up to 98% of goods.
The other 2% of goods would potentially avail of rebates from any tariffs, according to RTÉ’s Tony Connelly, who first reported the plan.
‘No Belfast mini-EU embassy’
The “at risk” goods problem would be almost entirely solved if there was a trade deal between the EU and UK, eliminating tariffs on all goods.
But in the absence of a trade deal the trusted trader scheme would minimise the issue.
The government also confirmed there will be an EU presence in NI after 1 January, but Mr Gove said it would not amount to a “Belfast mini-embassy”.
“The EU officials will not have any powers to carry out checks themselves,” he said, adding there would be “sensible and practical” cooperation and data sharing on both sides.
Downing Street said it remained committed to peace and prosperity in Northern Ireland and that NI Secretary Brandon Lewis would shortly set out further measures of financial support to help businesses and communities in NI.
What is the Northern Ireland Protocol?
Its fundamental purpose is to prevent a hardening of the land border between Northern Ireland and the Republic of Ireland.
It does that by keeping Northern Ireland in the EU’s single market for goods and by having Northern Ireland apply EU customs rules at its ports.
That means goods arriving from Great Britain are supposed to be checked and controlled at Northern Ireland’s ports from 1 January.
This arrangement will apply whether or not a wider trade deal is agreed.
It will also mean when relevant EU laws are amended or new ones are drawn up, they will apply in Northern Ireland.
Under the plan, NI will leave the EU customs union with the rest of the UK at the end of this year, but will continue to enforce the EU’s customs code at its ports.
BBC