The UK agriculture secretary has told his Stormont counterpart Edwin Poots to progress new border control posts (BCPs) "without delay".
The BCPs at Northern Ireland's ports, which are used to check products arriving from Great Britain, are a requirement of the Brexit deal.
They are currently operating from temporary facilities.
However, the EU said work needs to begin urgently on permanent premises.
Stormont's Agriculture Minister Edwin Poots, from the Democratic Unionist Party (DUP), has been resisting this but the UK government has said the work must be done.
In a letter to Mr Poots, sent earlier this month, Agriculture Secretary George Eustice said: "Your responsibilities include providing the necessary facilities for the conduct of checks."
The letter said Mr Poots must also provide "sufficient appropriately qualified personnel for these purposes".
"I look to you to progress these without delay," it added.
Mr Eustice also reminded Mr Poots that while overarching responsibility for international relations rests with the government in Westminster, delivering the practical requirements "falls to you and your department".
He said he had also asked officials to stop recruiting BCP staff.
That move was opposed by other members of the Northern Ireland Executive and its is understood that the interim Northern Ireland Attorney General advised that Mr Lyons should have brought the decision to the Executive.