Taoiseach Leo Varadkar has said it is his view that British citizenship laws are out of step with the spirit of the Good Friday Agreement.
He was commenting in the Dáil during Leaders' Questions on the case of Emma DeSouza, an Irish woman from Derry who lost a challenge by the British Home Office on its ruling that she is British by birth.
The Taoiseach said the Good Friday Agreement was clear and said that people in Northern Ireland have the right to be British, Irish or both.
He said that it was his view that Ms DeSouza was an Irish citizen and had an Irish passport.
Mr Varadkar said the issue has been raised by Tánaiste Simon Coveney with the Northern Secretary, Julian Smith, and he said he would raise it again this week with British Prime Minister Boris Johnson.
Sinn Féin's Mary Lou McDonald said the British Home Office must acknowledge the birthright provision of the Good Friday Agreement and allow Ms DeSouza to assert her full rights as an Irish and EU citizen.
Ms McDonald said the Home Office must understand that it was unacceptable to pursue a woman through the courts for simply being Irish.
She told the Dáil that the 20 years after the signing of the Good Friday Agreement the British government had failed in its responsibilities as co-guarantor.
Ms McDonald said simply raising the issue was not sufficient and she said a resolution was needed in a speedy fashion.
The Taoiseach said the Government would continue to uphold the Good Friday Agreement in letter and spirit.
He said the Government would continue to respect the fact that people in Northern Ireland have the right to be British, Irish, or both.