The leader of the SDLP described Brexit as a "national emergency" as he launched his election bid in Derry.
Colum Eastwood will run as a candidate in the Foyle constituency where his party lost its long-held seat to Sinn Féin in 2017.
Elisha McCallion defeated former SDLP chief Mark Durkan by just 169 votes.
This morning, Mr Eastwood said he will contest the Foyle seat for the expected December 12 poll to speak up for Derry over Brexit.
"Brexit is a national emergency. It threatens people, businesses and communities across this island, but particularly in Derry where travelling across the border for work, to visit family or to socialise is a basic part of our lives," he told a press conference at the Playhouse theatre in the city.
The @SDLPlive @columeastwood set to stand for the Westminster election in Foyle pic.twitter.com/PPQ27QupOt
— Leona O'Neill (@LeonaONeill1) October 30, 2019
"We know the scale of the challenge we're facing. The time for talking is now over; now it's time to take control of our own future, stand up for ourselves and vote Boris Johnson's Brexit down.
"This is a time for leadership. I understand that, when the stakes are this high, you have to be prepared to take on the uncomfortable and the unprecedented."
Mr Eastwood confirmed that, if elected, he will vote against Brexit in the House of Commons.
Ms McCallion does not take her seat at Westminster in line with Sinn Féin's longstanding abstentionist policy.
Mr Eastwood added: "At a time when communities like ours should be setting the agenda, we need our first team on the pitch. Instead, Derry is on the sidelines. That's not acceptable.
"This is a defining election. It is a moment of choice and a moment for change. I am not content to continue with the direction of travel. I will not sit idly by as our interests are undermined. Brexit can be stopped at Westminster. SDLP MPs will vote to stop Brexit."
Sinn Féin confirmed last month that Ms McCallion will be running to retake the seat if a general election is called.
