TAOISEACH Leo Varadkar has warned that soldiers may return to the border if Brexit goes "very wrong".
He said in a worst-case scenario there could be a return of armed customs posts after the UK leaves the European Union.
Mr Varadkar told Bloomberg TV the border at present is "totally open" but if things went "very wrong" it would "look like 20 years ago".
Asked to describe what a hard border would look like in a worst-case Brexit outcome, Mr Varadkar said: "It would involve customs posts, it would involve people in uniform and it may involve the need, for example, for cameras, physical infrastructure, possibly a police presence or army presence to back it up."
His comments were criticised by DUP MP Gregory Campbell as "deeply unhelpful", while Sinn Féin president Mary Lou McDonald said Mr Varadkar's remarks were "reckless and irresponsible".
A government spokesman later issued a statement to clarify that Mr Varadkar was not referring to the Irish Army.
"The taoiseach made it clear in the interview that the government is determined to avoid a no-deal scenario and the consequent risk of a hard border," he said.
"He was asked to describe a hard border, and gave a description of what it used to look like, and the risk of what it could look like in the worst-case scenario.
"He was not referring to Irish personnel and the Irish government has no plans to deploy infrastructure or personnel at the border."
The picture became further confused later yesterday when a senior Fine Gael politician indicated that Irish troops could be deployed to the border in the event of a crash-out Brexit.
Asked whether British or Irish troops would have to serve on the border in a worst-case scenario, Fine Gael's Brexit spokesman Neale Richmond said "probably both".
"International obligations could see both the British and Irish governments forced to put customs posts and those custom posts might need to be protected by armed guards. That is something that is the worst-case scenario," he told BBC Radio Ulster.
Mr Varadkar also said Ireland is being "victimised" in the Brexit process.
He said the government would not be giving up on the 'backstop' plan for promises that the border issue would be rectified at a later date.
"We're the ones already giving," Mr Varadkar said.
"The UK wanted a review clause in the backstop and we agreed to that, the UK wanted a UK-wide element, so why is it the country that is being victimised is the one that's always asked to give?"
