SINN Féin MEP Martina Anderson has said Theresa Villiers should continue to follow the lead of UKIP and resign.
Earlier today, Nigel Farage announced he was standing down as leader of the UK Independence Party (UKIP).
Mr Farage said his “political ambition has been achieved” with the UK having voted to leave the EU.
He said the party was in a “pretty good place” and said he would not change his mind about quitting as he did after the 2015 general election.
Following his resignation, Ms Anderson said: “The latest resignation by someone who campaigned for a leave vote seems to indicate they are losing confidence in the result in the face of the growing realisation of the impact of leaving the EU.
“UKIP have set the agenda of the Tory party throughout this whole process and now Theresa Villiers should follow the lead of Nigel Farage and resign also.
“The people of the north voted in favour of remaining in the EU and that democratically expressed vote needs to be respected.
“She has no legitimate claim to represent the best interests of the people of the North on the EU and, as a result, her position has become untenable.”