SDLP assembly member Nichola Mallon is "delighted to be given the opportunity" to become the party's deputy leader.
The north Belfast politician has been endorsed by the SDLP's parliamentary assembly group to take on the role, which will be formally ratified at the party's annual general meeting next month.
Ms Mallon, who was elected as an MLA in 2016 and has served as Belfast Lord Mayor, said her election came at a "critical moment for our politics".
"The challenge we all face is to forge a society based on a positive accommodation of difference and diversity," she said.
"That challenge is made all the more important following the Brexit Bill vote last night.
"I'm delighted to be given the opportunity to step up and take on that work within the SDLP and with political parties and civic society across this island."
SDLP leader Colum Eastwood said he was delighted Ms Mallon had received the "unanimous endorsement" of the party's parliamentary assembly group.
"Nichola’s unyielding compassion and fierce commitment to social justice and defending the rights of the most vulnerable in our society has made her an outstanding public representative," he said.
"I have no doubt that she will serve the party well as our new deputy leader.
"As we enter a period of immense instability on the island and across this continent, there will be an inevitable shift in politics.
"More than ever, we have to be outward looking, we have to be open to the changes on this island and open to its opportunity. I have given Nichola special responsibility undertake that work on behalf of the SDLP.
"The party is incredibly proud that Nichola is stepping up to this new leadership role."
