The SDLP will not be contesting the Westminster seat in North Belfast for the first time in the party's history.
It is one of three constituencies which it will not fight in a bid to secure the seat for pro-remain candidates.
The other two constituencies are East Belfast and North Down.
SDLP deputy leader Nichola Mallon said the objective "must be to return as many pro-Remain MPs who will take their seats and vote to stop Brexit".
The North Belfast MLA added her party "must also seek to weaken those who have cast the interests of Northern Ireland aside for five minutes of influence with a Tory government that has been bad for our communities".
Ms Mallon said that meant "removing pro-Brexit, pro-Boris DUP MPs where possible".
Analysis: Jayne McCormack, BBC News NI political reporter
This election campaign has only officially begun but battle lines are already being significantly redrawn.
Northern Ireland's parties have always been quick to say they "don't do" pacts, but that argument becomes much more difficult to take seriously now.
Parties standing aside for each other in certain constituencies is nothing new; it is a tried-and-tested - and sometimes very successful - strategy of quid pro quo.
However, the Ulster Unionists have done a massive u-turn just days after insisting they wouldn't be standing aside anywhere this time.
And the SDLP, which has often criticised Sinn Fein for not taking their seats in Westminster, now argues that the tactics must be different this time.
Brexit has certainly shifted the dynamics in this election, what's not clear is how voters will respond to that and what it will mean for the 18 seats up for grabs.
The SDLP is not the only party which has decided not to stand for election in North Belfast.
On Sunday, the Ulster Unionist Party confirmed it will not field a candidate in the constituency where the choice was the sitting DUP MP Nigel Dodds or "an abstentionist MP" from Sinn Féin.
UUP leader-elect Steve Aiken had initially ruled out a DUP election pact but later came under pressure from high-profile unionists who said the UUP must avoid splitting the unionist vote in North Belfast.