The UK is facing a constitutional crisis after the results of survey on regional independence showed a majority of Northern Ireland voters - 51% to 44% - want a border poll within the next five years.
A new poll from the Sunday Times 47% of those surveyed would back remaining in the UK, while 42% are undecided, showing unionists hold only a slender lead on those who want a united Ireland now.
Another 11% are undecided on the issue.
The LucidTalk survey carried out in Northern Ireland found that among those aged under 45, supporters of Irish reunification outnumber those who want to stay in the UK by 47% to 46%
Northern Irish voters also think there will be a united Ireland within 10 years by a margin of 48% to 44%.
The study was based on 2,392 people aged over 16 surveyed between January 15 and 18 this year.
Of those asked in England, only 31 percent would be upset at Irish unification, with 20 percent pleased and 37 percent not bothered.
The Scottish section of the survey found that 42 percent of those asked would not be bothered by a united Ireland, 29 percent would be pleased and 21 percent would be upset.
The only time a border poll was held in Northern Ireland was in March 1973, but it was boycotted by nationalists. The voter turnout was 58 percent, with 98 wishing to remain part of the UK.
A four-country survey based on separate polls in Scotland, Northern Ireland, England and Wales found that a majority of voters in Scotland and Wales want referendums on their unity with the United Kingdom.
Cabinet ministers, chaired by Michael Gove, and the secretaries of state for each devolved nation met last week to discuss plans for a new campaign to build the case for the union.
The surveys come a short time after former Conservative chancellor George Osborne said most people in England would not care if voters cast a majority for a united Ireland.
He wrote in the Evening Standard: “By remaining in the EU single market, it (Northern Ireland) is for all economic intents and purposes now slowly becoming part of a united Ireland.
“Northern Irish unionists always feared the mainland was not sufficiently committed to their cause. Now their short-sighted support for Brexit (and unbelievably stupid decision to torpedo Theresa May’s deal that avoided separate Irish arrangements) has made those fears a reality.
“It pains me to report that most here and abroad will not care.”
The poll shows voters expect Scotland to become independent within the next decade by margins far in excess of two to one in England, Wales and Northern Ireland.
The Scottish poll, conducted by Panelbase, found the SNP is on course for success in the Scottish parliament elections due in May - which is likely to be the trigger for a new political crisis.
The piece suggested Nicola Sturgeon would use this to ask for a new independence vote, but it quotes senior government sources who say Boris Johnson will flatly refuse that demand, with the UK government having little intention of offering early concessions on further devolution.
In the 2014 referendum, Scotland voted against independence by 55.3 percent to 44.7 percent, with a turnout of 84.6 percent.
YouGov, which conducted the surveys in Wales and England, found that support for Welsh independence has grown to 23%, up from the teens five years ago.
SDLP leader Colum Eastwood said the polls place an obligation on parties to set out a new vision for the future that meets the needs of all.
A decade of UK government policy that has stripped public services, removed opportunity from some communities and forced a new constitutional reality on the people of Northern Ireland and Scotland has had profound consequences, he said.
"I genuinely believe that our interests are best served in a new Ireland and that’s reflected in the hours of conversations we have held with people across this island," he said.
"The coming conversation places a solemn obligation on those of use who believe in a new future to engage with every community, sector and generation to set out our vision for a country and a society that meets the needs, hopes and aspirations of all our people."
He added: "The United Kingdom may be coming to an end but we are all called to build a new future together."