The power to grant or deny freedom of movement for EU nationals in Northern Ireland after Brexit should be devolved to Stormont, peers have said in a report.
The House of Lords EU Committee recommended a draft bilateral treaty between the UK and Ireland to protect the 60 billion euro trade between the countries, subject to approval from Europe during exit negotiations.
Peers warned that "efforts of all those who have worked so hard for peace and good relations across these islands" could be undermined if the UK fails to pay enough attention to the effect Brexit will have on Ireland.
The UK's only European land border is between Northern Ireland and the Republic and the committee said Brexit was a "huge challenge" for Ireland.
The report - Brexit: UK-Irish Relations - called for continuation of the open land border between the UK and Ireland and ease of movement across the sea boundary between Northern Ireland and the rest of the UK.
They said: "The key aspects of that agreement should include... providing the Northern Ireland Executive with the right to make decisions about the free movement of EU nationals within its jurisdiction."
The committee also recommended:
- Maintenance of the Common Travel Area, free movement within it for UK and Irish citizens, and their right to reside and work in both countries.
- Retention of the right to Irish (and therefore EU) citizenship for the people of Northern Ireland.
- Reaffirmation by both governments of their commitment to the Good Friday Agreement and continued support for cross-border cooperation.
- Continued access to EU funding for cross-border projects.
The UK government has yet to determine whether it will seek to impose restrictions on the free movement of EU citizens to live and work in the UK, the report said.
The EU's remaining 27-country bloc is reluctant to grant the UK free trading rights if restrictions are imposed on the movements of its citizens.
A Government spokesman said: "The Government is working to secure a deal that works for the whole of the United Kingdom. Ministers are acutely aware of the deep links between the UK and the Republic of Ireland.
"There is already a common travel area between the two countries, created many years before either was a member of the European Union.
"We are clear we do not want a return to the borders of the past, no unnecessary barriers to trade and no obstacles between Northern Ireland and the rest of the UK. The Government will consider this report carefully and respond fully in due course."