Micheál Martin told Irish broadcaster RTÉ “trust has been eroded” by the move by Prime Minister Boris Johnson.
“The stakes are higher now because of the British action,” he said.
Critics have said the proposed Internal Market Bill, published on Wednesday, would “tear up” the existing withdrawal agreement.
The bill proposes no new checks on goods moving from Northern Ireland to Great Britain.
It gives UK ministers powers to modify or “disapply” rules relating to the movement of goods that will come into force from 1 January, if the UK and EU are unable to strike a trade deal.
To read the full article, please click here.