The threat of deportation to Rwanda is causing migrants to head for Ireland instead of staying in Britain, Ireland's deputy prime minister told a British newspaper on Friday.

British Prime Minister Rishi Sunak's flagship programme to send asylum seekers to Rwanda if they arrive in Britain illegally was approved by parliament earlier this week and the government wants the first flights to take off in 10-12 weeks.

Deputy Prime Minister Micheal Martin told The Daily Telegraph that the policy was already affecting Ireland because people were "fearful" of staying in Britain.

He said asylum seekers were seeking "to get sanctuary here and within the European Union as opposed to the potential of being deported to Rwanda".

The border between Northern Ireland, which is part of the United Kingdom, and the Republic of Ireland, a European Union member, is the only land border between the UK and the EU since Britain left the bloc.

That border is effectively open, with no immigration checks - a key condition of the deal that took Britain out of the EU in 2020, designed to avoid creating a flashpoint given the island's sectarian history.

Earlier this week, Ireland's Minister of Justice Helen McEntee told a parliamentary committee she estimates that more than 80% of people applying for asylum in Ireland are coming from Britain over the land Border with Northern Ireland.