By Michael McHugh, Press Association
The nationalist SDLP has voted by more than two to one to back a new partnership with Ireland's main opposition party.
Members gathered in Newry in Co Down on Saturday to confirm leader Colum Eastwood's proposed link-up with Fianna Fail.
An alternative, supported by many founding grandees, was defeated.
Mr Eastwood said: "What we have agreed today is a policy partnership, to try to deal with the very real problems, the crises that are in our politics today.
"It is two parties working together for the betterment of this country, that is what we have committed to, that is what we have agreed, that is what we have a mandate for and that is all we are doing today."
The leadership's proposal was carried by 121 votes to 53 for an alternative tabled by the Lurgan branch, a margin of 70%.
The SDLP has badly trailed Sinn Fein in the polls over recent years.
Mr Eastwood said: "We have a huge challenge, we know that, politics does better, people do better, when the SDLP do well.
"We are not pretending this is a quick fix.
"We are not talking about building for the next election, we are talking about building for the next generation, that is the work we are recommitting to today.
"It is a hard slog, it will be a lot of hard work, but people look at the alternatives and the fact that we have had no government in this place for two years.
"When we look at the fact that we have Brexit and the only MPs fighting our corner are independent unionist MP Sylvia Hermon.
"The people representing us in Westminster either don't turn up or vote against the wishes of the people of Northern Ireland.
"That is not good enough, it is time to see a change, we are committed to making that change and looking forward to rolling our sleeves up, to getting around the doors and working together to make sure we see that happen."
The SDLP and Fianna Fail previously proclaimed the move a step towards breaking the cycle of "vacuum and division" which had failed people in Northern Ireland during the two years since political powersharing collapsed.
Fianna Fail is a larger southern party which its leader Micheal Martin said would give electoral resources and know-how as the SDLP bids to bolster faltering fortunes north of the border.
A merger to create an all-island party is not currently envisaged but Brexit has prompted republican calls for a referendum on Irish unity after a majority in Northern Ireland voted to remain in the EU alongside their southern neighbours.
Dissenting voice South Belfast Stormont Assembly member Claire Hanna said: "I came believing an exclusive arrangement was not a good idea, I have not changed my mind."
The SDLP has no representation at Westminster and 12 members of the 90-strong Stormont Assembly in Belfast.
It has promised a partnership with Fianna Fail based around shared policies on issues like Brexit and Irish unity.
Stormont has been becalmed amid a row between former powersharing partners Sinn Fein and the DUP.
Mr Eastwood said the change aimed to restore public faith in politics.
Irish Labour Party leader Brendan Howlin said: "After decades of co-operation with SDLP as our sister party, it's sad to see them moving into the arms of Fianna Fail."
In a statement the party said they were disappointed.
"The consequences of the partnership decision will now be carefully considered by the Labour Party in the coming weeks, and in consultation with our colleagues in the Party of European Socialists.
"The Labour Party remains committed to supporting those who wish to maintain Labour politics and the social democratic tradition in Northern Ireland."