It was made clear during Brexit negotiations there would be checks on goods from Great Britain into Northern Ireland, Simon Coveney has said.
Boris Johnson has said the only checks would be on British exports to the Republic of Ireland going via NI.
But his deal means checks on some goods even if they are not going onwards to the Republic of Ireland.
The tánaiste (Irish deputy PM) said: “It was very clear when the deal was done.”
Speaking in Brussels, Mr Coveney said there would be east-west checks on goods coming into Northern Ireland, while goods going in the other direction would be limited to export declarations.
On Sunday, Mr Johnson denied there would be any checks on goods moving from Northern Ireland to Great Britain.
‘Many, many hours of discussion’
“Goods coming from Great Britain into Northern Ireland will need to have some checks to ensure that the EU knows what is potentially coming into their market through Northern Ireland,” Mr Coveney said.
“And, you know, we spent many, many hours of discussion in terms of trying to get that right.”
He added concluding a trade deal and other agreements with the UK by the end of 2020 was a “tall order”.
Mr Johnson has said the UK will fully exit the EU by December 2020 if he wins the election and MPs approve his plan.
The UK has to decide by July 2020 if it wishes to extend the period.
The PM did not directly comment on the report when asked.
But Mr Johnson instead said his plan was a “great deal” for both Northern Ireland and the rest of the UK, and would “give the country real momentum”.
He has has pledged to finalise leaving the EU by 31 January, and said a trade deal will be done with the bloc by the following December.
However, he has also said if no deal is done by that deadline, the UK will still leave – meaning all transition agreements will come to an end by the close of 2020.