Sinn Fein president Mary Lou McDonald has been heavily criticised after marching in the US behind a banner reading: 'England get out of Ireland'.
It happened during the annual St Patrick's Day parade in New York on Saturday. Sinn Fein posted an image of her on social media, tagging in the Dublin TD, stating: "No explanation needed."
However, rival politicians also took to social media to demand an explanation from Sinn Fein, with many unionists saying the banner was "anti-British".
DUP deputy leader Nigel Dodds said: "It’s clear that republicans don’t do explanations. Neither do they do apologies. They’ve never explained let alone apologised for the terror their armed wing conducted for so long.
"There certainly has never been any apology for the IRA’s indiscriminate bombing, sectarian murder or wilful use of torture, said Mr Dodds.
"Like truth and respect, explanations are demanded, but never offered by Sinn Fein."
DUP MP Gregory Campbell said the slogan "sums up" Sinn Fein's attitude to explanations, truth and respect.
"When slogans such as 'Brits out' or 'England out of Ireland' are used, the unionist community are well within their rights to see themselves as the intended focus," he said.
"The 'British presence in Ireland' is the unionist population in Northern Ireland.
"The republican focus on 'Brits' in the city of Londonderry saw thousands of unionists move out en masse from the Cityside as the IRA began their 'war'.
"It's clear that republicans don't do explanations. Neither do they do apologies.
"They've never explained, let alone apologised, for the terror their armed wing conducted for so long."
Tanaiste Simon Coveney accused Ms McDonald of poor leadership and of being an embarrassment.
He tweeted: "Mary Lou McDonald this is NOT leadership - it's offensive, divisive and an embarrassment - grow up, this is NOT Ireland in 2019! We are better than this!"
Former Victims' Commissioner Patricia MacBride told BBC NI's Sunday Politics programme that she understood the sign gained prominence in New York in the early 1980s.
"I think it was very much of its time and needs to be consigned to history at this point in time and moving forward," she said.
Ulster Unionist leader Robin Swann MLA said: "Once again Mary Lou McDonald, as president of Sinn Fein, has shown them up for what they are really all about, as she posed behind a banner which was highly offensive and wrong on so many levels.
"It demonstrated that bigotry and hypocrisy were alive and well within their version of republicanism.
"It is clear that when Sinn Fein talk about respect, honesty and integrity, that they are as sincere as Gerry Adams using equality as a Trojan horse to attack unionists.
"Their words about rights are only a veneer to hide their true intention."
Speaking on BBC radio, Alliance leader Naomi Long hit out at what she called Sinn Fein's "Anglophobia".
She added: "Politicians can get giddy on the kind of high of hanging around with people in the Irish-American lobby, who perhaps don't see the subtle distinctions that we are aware of back home.
"I think that anti-English sentiment, Anglophobia, is one of the last permissible kinds of xenophobia that we accept.
"And I don't think it's good enough."
The East Belfast MLA said the banner "sends out a hostile and offensive message to anyone English or of English extraction on this island".
Sinn Fein accused the party's critics of playing politics.
"The most divisive and offensive act on this island for almost the last 100 years has been the partition of Ireland," the party said.
"It should come as no surprise that Sinn Fein wants a new united Ireland under the provisions of the Good Friday Agreement.
"The faux outrage of some of our political opponents owes more to the silly season of a holiday weekend and petty political point-scoring.
"However, if Simon Coveney and the government is serious about achieving a new and agreed united Ireland, then he should immediately convene an all-Ireland forum on Irish unity." Belfast's Sinn Fein Lord Mayor Deirdre Hargey also defended the banner. "It's no surprise that republicans feel that the future of Ireland should rest with the people who live in Ireland," she told the BBC.
"Partition happened here almost 100 years ago. That was the role of England, little England attitudes, and the Westminster Government.
"That's what the banner signifies in my view, in terms of that issue of partition."