SDLP leader Colum Eastwood has suffered a setback ahead of defending his Westminster seat in the forthcoming general election with the departure of his key adviser.
Derry-born Ruaidhri O'Donnell, who joined Mr Eastwood's backroom team soon after the SDLP reclaimed the Foyle seat in 2019, is taking up a management post with manufacturer Marshall in England.
The Queen's University graduate previously worked for the NI Stronger In Europe campaign and the Labour Party.
His decision to quit comes as Mr Eastwood prepares to defend his seat against a reinvigorated Sinn Féin in Derry.
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Recent polling has indicated support for the SDLP is waning, while a Sinn Féin purge of former elected representatives and associates in the north-west is expected to strengthen the party's electoral prospects following a disastrous Westminster election four years ago that saw Mr Eastwood retake Foyle with a majority of more than 17,000.
Mr O'Donnell's departure coincides with the adoption of a new SDLP constitution, though the two developments are unrelated.
At a meeting in Belfast on Saturday, the revised constitution received unanimous support from delegates.
The changes in the party's constitution reflect recommendations made in a report by South Belfast MP Claire Hanna in the wake of last year's assembly election, in which the SDLP lost four seats.
They include the creation of 18 new branches in each of the north's constituencies and the dropping of the deputy leader's position, most recently held by Nichola Mallon.
A statement from the SDLP said the party was "engaged in a process of reorganisation and renewal" in preparation for the next Westminster election and its role as opposition in a restored assembly.
"The changes unanimously backed by party members last weekend represent the biggest shakeup of our internal structures in over a decade and place activism at the heart of the new SDLP organisation," the party said.
"As part of this process the party will be making a number of appointments in the coming weeks that will grow our campaigning capacity, ensuring we are fighting fit to provide a radical alternative to a new executive and to play our part in removing this Tory government from power."