And she said that Sinn Féin will be intensifying its diplomatic efforts in Europe in the critical weeks ahead.
She was speaking as discussions between the EU and the British Government continue in Brussels this weekend in an effort to break the logjam over the Irish backstop.
Martina Anderson said: “As we enter into a crucial stage in the Brexit process with further negotiations in Brussels it is essential that the backstop is maintained.
“It provides a legal guarantee to the people of the north that there will be no hardening of the border and that must not change.
“The Tory Brexiteers are again attempting to seek to limit the backstop and the role of the ECJ. That is unacceptable.
“Tory Brexiteers and the British Parliament must not be allowed to unravel it.
“The EU and the Irish government need to stand firm on what has already been agreed.
“In the critical weeks ahead Sinn Féin will be intensifying our diplomatic efforts in Europe to ensure the backstop is protected and building support for a referendum on Irish unity,” she added.