Peace in Ireland is more important than relationships that could affect economic growth, Tánaiste Simon Coveney has said.
He also warned the British government that Ireland will not be the “casualty” of divisions in the Conservative Party.
Mr Coveney warned the Tories against a strategy that may be "about keeping a party together that for 30 years has been torn apart" by the UK's relationship with Europe.
“If that what this is about, I cannot allow that agenda make Ireland the casualty of,”he said.
In a speech in Dublin on Wednesday, Mr Coveney criticised the decision of British prime minister Theresa May to support a vote in the House of Commons calling for the backstop, the insurance policy to avoid a hard border after Brexit, to be replaced.
The Tánaiste mounted a strong defence of the backstop, which would see the UK remain in a common customs area with the EU, with add ons in terms of customs and regulations for Northern Ireland to keep the Irish border open, if there is no future trade deal between the EU and the UK.
Mr Coveney said the backstop and issues relating to the peace process were difficult to deal with during Brexit negotiations and took a long time to reach a compromise on.
“That is why the backstop, and the peace process and the border issues…have been so difficult to deal with and took so long to get compromises on.”
On peace, Mr Coveney told a meeting of the Institute of International and European Affairs (IIEA) in the Gresham Hotel: "There are some things that are more important than economic relationships, and this is one of them."
Mrs May has said she will return to Brussels to seek changes to the backstop, the element of the Brexit withdrawal agreement that is the main stumbling block to the deal passing Westminster.
The motion she backed in a House of Commons vote on Tuesday, and which won a majority in the house, called for the backstop to be replaced by unspecified alternative arrangements.
Mr Coveney said a legally operable backstop cannot be given up for hopes that the Border can be kept open by some other method.
“These hopes have already been tested in negotiations and have come up short,” he said. He said the vote in the Commons “signals a turning point of a British prime minister on this issue” and said that is why it has had “such an impact here” and in Northern Ireland.
He called on the UK to listen to all political parties in Northern Ireland and not just Mrs May’s confidence and supply partners in the DUP, saying it is “all the more critical”.
Mr Coveney said he has been equally critical of Sinn Féin’s call for a referendum on Irish unity to take place as a result of Brexit.
The Tánaiste also said that any replacements for the backstop could be tested but insisted the “backstop has got to be there”.
He said it “ceases to be a backstop” if it is subject to a time limit with no clear answer on what comes when that time limit ends.
Mr Coveney also said that trust between Ireland and the British government had been put under strain by the House of Commons vote to replace the backstop.
He also said there is trust between Ireland and Britain, but added: “Some of it was tested last night.”