THERESA Villiers has been accused of undermining the credibility of the secretary of state's role by taking to the streets of east Belfast to campaign alongside Vote Leave supporters.
The pro-Brexit cabinet member joined East Belfast MP Gavin Robinson and DUP MLA Christopher Stalford last Thursday evening as they canvassed households ahead of next week's referendum.
Ms Villiers's ability to act in the interests of Northern Ireland while supporting a break with Brussels has been questioned by those who believe the region is overwhelmingly in favour of remaining in the EU.
Pro-Remain Labour MP Conor McGinn, who represents St Helen's in northern England but originally hails from Crossmaglen in south Armagh, claimed the secretary of state's appearance on the doorsteps was another example of poor judgement she had displayed throughout the referendum campaign.
"It was ill-advised and will raise further questions about her judgement," said the close ally of shadow secretary of state Vernon Coaker.
"Some of what she has said and done during the course of the referendum campaign has badly undermined the credibility of the secretary of state's role and damaged confidence in her ability to fulfil it."
SDLP leader Colum Eastwood also claimed Ms Villiers's decision to actively campaign in the north was at variance with assurances she had given.
"It’s quite clear that despite giving the SDLP assurances that she would not campaign as the secretary of state for Northern Ireland, that Theresa Villiers has decided to abuse her position anyway," he said.
"Like all of the fantasy promises made by Leave campaigners, it too was paper thin."
But Vote Leave regional co-ordinator Lee Reynolds said Remain supporters would not dictate who campaigns to leave the EU.
"The Remain camp have used both NIO minister Ben Wallace and the shadow secretary of state Vernon Coaker in their campaigning and Vote Leave accepts their participation as a legitimate part of the referendum debate," he said.
"Theresa Villiers following her own political judgement and conscience is equally so."
Mr Reynolds claimed the Remain campaign's "real problem" was that Ms Villiers was a "prominent and credible figure".
Meanwhile, a former head of the World Trade Organisation has warned that a Brexit would be "an act of wanton destruction" on the north's economy.
Peter Sutherland said the region would suffer more than Britain in the event a Leave vote.
Speaking on the BBC on Sunday, he claimed UK withdrawal from the EU would cause a "grave, serious and prolonged period of great uncertainty".
The secretary of state has insisted a Brexit would create "fantastic opportunities" for Northern Ireland.
