Gerry Adams has said tonight's vote by the British Parliament on amendments to the European Union (Notification of Withdrawal) Bill, shows that "the British government does not care one iota for the people of the North."
The parliament voted against an amendment which said the British government must take the Good Friday Agreement into account when triggering Article 50
The amendment, proposed by the SDLP, was voted down by British MPs by 327 votes to 288, a majority of 39.
The Labour party, the Liberal Democrats, the SNP, Plaid Cymru backed the amendment, and they were joined by Independent Unionist Sylvia Hermon and former Conservative chancellor Kenneth Clarke.
The DUP, the Ulster Unionists and Ukip supported the Conservatives in voting against the amendment, along with five pro-Brexit Labour MPs, including Kate Hoey, a member of the Northern Ireland Affairs Committee.
The European Union (Notification of Withdrawal) Bill to pave the way for the formal Brexit process to begin under Article 50 of the EU treaties cleared the British House of Commons without being amended.
The Sinn Féin President Gerry Adams TD said it is time that the Taoiseach stopped playing junior partner to the British Government.
Mr Adams said: "Tonight, the Tory party voted down an amendment in the Article 50 debate which would have blocked any changes to the Good Friday Agreement.
"Two weeks ago, I learned that the Good Friday Agreement will be destroyed if the North is dragged out of the EU.
"This decision confirms my worst fears. The British government does not care one iota for the people of the North.
"An Taoiseach puts great faith in statements from the British Government; he did so again in the Dáil today in response to questions from me.
"Tonight’s vote shows the short sightedness of the Taoiseach’s approach
"Mr Kenny has to stop playing junior partner to the British Government. The Good Friday Agreement must be protected. That is his duty."
The Bill will now pass to the UK's House of Lords, where the stages - second reading, committee (when substantive amendments can be made) and third reading - are repeated.
The British Government could find life more tricky in the upper chamber, where the Bill will be introduced on February 20, because it does not have a majority.
Labour in the Lords has already said it will examine but not block the Government's Brexit plans, although some individual peers are likely to register their opposition.
But the Liberal Democrats are determined to guarantee a fresh referendum on the final deal, protect single market membership and guarantee the rights of EU citizens in the UK.
The party has 102 peers, compared with 253 Tories, out of a total 805.
The Bill is expected to complete its passage through the Lords by Tuesday March 7 but if peers have made amendments, it will return to the Commons, where MPs will debate whether to keep the changes or get rid of them.
This procedure, known as "ping-pong", would see the Bill repeatedly move between the Commons and the Lords until an agreement is reached on the final text.
Ping-pong seems the most likely stage for the Bill to be held up, as peers could become emboldened with time running out for the Government to hit its timetable of triggering Article 50 by April.
But members in both Houses will be acutely aware that appearing to frustrate the progress of the Bill would risk accusations that they are going against the will of the people expressed in last year's referendum.
And unelected peers have also been warned by a Government source that the Lords will face an "overwhelming public call" to be abolished if it attempts to frustrate progress.
The fact the legislation passed through the Commons without being amended also weakens peers' hands.