Gerry Adams has accused Fine Gael and Fianna Fáil of being mesmerized by the British during Brexit negotiations.
The Sinn Féin leader says Ireland needs to look after our own national interests when the UK leaves the EU.
He is now urging the Taoiseach to seek a special designated status for the North to protect its European funding.
Last night MPs gave the Prime Minister Theresa May the green light to formally start the process of exiting the union.
Mrs May has said maintaining a common travel area with the Republic will be an "important priority in talks ahead".
Gerry Adams, however, says his party remains concerned about a potential return to a hard border between the Republic and the six counties.
Deputy Adams told Pat Kenny: "Our biggest concern in this particular vote is if one part of this island leaves the European Union, then you will see the return of a hard frontier.
"My big criticism of how the Taoiseach has dealt with this - and indeed how Fianna Fáil has dealt with this - is that they have been mesmerised by what the British may or may not do."
He also suggested: "I don't want to see British rule in any part of our country, and we've a big challenge to persuade those who do is that there's a better option in an agreed Ireland. That could be one of the consequences of this Brexit issue.
"Arguably Theresa May has inherited a situation. It was David Cameron's stupidity that landed them in this position, trying to fend off the extreme-right wing.
"But we are where we are. What Sinn Féin is saying very, very clearly to the Taoiseach and Irish Government is look after our national interest," he added.
However, he also stressed that armed conflict in the North is 'over, its done with'.
