Former Irish premier Leo Varadkar said that Irish unity would become “centre stage” if Reform UK leader Nigel Farage was elected UK prime minister.
Mr Varadkar, who stood down as taoiseach in April last year, said it is possible Mr Farage will be prime minister in four years or nine years time.
He described British politics as “very volatile”.
Reform made big gains in local elections in England and Wales in May.
Mr Varadkar told BBC Northern Ireland’s The View programme, which will be aired on Thursday night, that he hoped Mr Farage is not the next British prime minister.
The former Fine Gael leader said if the Reform leader became prime minister, it would “change the pictures in terms of attitudes towards independence in Scotland”.
“I think it would change the views of some people in the middle ground in Northern Ireland (towards Irish unity),” he said.
“It isn’t just because a right-wing nationalist government in London would want to bring the UK and Northern Ireland away from Europe. It is other things as well.”
He also claimed that councils run by Reform in England were preventing people from flying Pride or progress flags.
Mr Varadkar added: “I don’t think most people in Northern Ireland would like that.
“If that’s the kind of government they had in London versus a government in Dublin that was very different, it might make them more likely to vote yes to unification,” he added.
“I do want to be very clear about this, it’s not something I hope happens.
“I hope it doesn’t happen.”
Mr Varadkar said he believes planning for a united Ireland should be happening, but that a date should not be fixed as the numbers to win are not in place.
He added: “I don’t think a united Ireland is inevitable, I think it’s something that we have to work towards.
“But I think there are a lot of factors that would suggest that we’re on that trajectory.
“Demographic factors, polling, even the most recent numbers showing that a very clear majority of younger people in Northern Ireland want there to be a new united Ireland.”
“I think that will carry true, and that’s why I think it’s something that we should plan for.”
He said Irish unity will not happen “by osmosis or by accident”.
“I think (it) has to be worked towards. I think those of us who believe in it have a duty to make the case for it,” he added.
“Look at the trajectory, and that is clear. We see it in elections. We see it in opinion polls. We see it in demographics.”
