Unionists were today preparing to go to the British government to stop the name of Derry being changed.
Nationalists on the city council have voted through a motion to remove "London" from the title.
But it will be the British government which will decide if the move goes ahead and the Queen who will formally have the last say as the name "Londonderry" was originally granted by Royal Charter.
Democratic Unionist Party members of the council are preparing to lead a delegation to Northern Ireland Office Minister Angela Smith who is responsible for the Department of Environment in Belfast.
Last night, Sinn Fein and the SDLP banded together in the council chamber to press through the name change motion.
DUP MP for East Derry Mr Gregory Campbell expressed disappointment at the vote and hit out at the SDLP for siding with the republicans.
"We are particularly disappointed that the party that have for many years held themselves up as a paragon of cross-community virtue have effectively said to unionists here: 'It doesn't matter about you.'
In 1984 nationalists changed the name of the council to Derry City Council. But changing the name of the city is more difficult.
London was added to Derry's name in 1641 when the then British queen - Elizabeth - gave the city over for development to the London Trade Guilds. The name was granted by Royal Charter and it will take an Act of Parliament to reverse it.
"The Secretary of State will need a chance to consider the motion that has been passed and its implications both for the people of the city and for the community as a whole in Northern Ireland."
PA