LONDON - Irish Prime Minister Micheal Martin warned Britain on Sunday it would be "very serious" if it enacted a new law to unilaterally change part of a Brexit deal to try to ease trade with Northern Ireland, and urged the government to resume talks.

"If this bill is enacted, I think we're in a very serious situation," he told the BBC.

"What now needs to happen is really substantive negotiations between the British government and the European Union."

(Reporting by Elizabeth Piper, Editing by Louise Heavens)