Journalist and civil rights campaigner Eamonn McCann is to run in the British general election.
The Bloody Sunday campaigner, who secured 2,257 votes in the 2003 Assembly election, is to bid for the Foyle seat as a Socialist Environmental Alliance candidate.
His candidacy will increase the intensity of an already fierce contest for former SDLP leader John Hume's seat. Mr Hume's successor as party leader, Mark Durkan is hoping to hold onto the seat though Sinn Féin general secretary Mitchel McLaughlin is considered a slight favourite.
According to the 2003 Assembly Election figures, the SDLP has a 1,532 lead over Sinn Féin. However, Mr Adams's party has made significant inroads into the SDLP's hold on the constituency, slashing the its lead from 11,550 in the 2001 general election.
Mr McCann's candidacy takes away 2,257 votes which both parties believed could be up for grabs. Under the single transferable vote system in the Assembly election, subsequent voting transfers from Mr McCann split evenly between the SDLP and Sinn Féin .
The Socialist Environmental Alliance will unveil its manifesto in Derry today with the party fielding five local government candidates, including Mr McCann, in the city.
Mr Durkan will today hand in his nomination papers at Derry's Electoral Office on the Strand Road. Democratic Unionist leader the Rev Ian Paisley will also hand in nomination papers today in North Antrim, which he has held since 1970.
Northern Ireland's Green Party will unveil its election manifesto with the help of Irish Green Party leader Trevor Sargent and Scottish leader Robin Harper in Holywood, North Down.
But the Ulster Unionists have put back plans for their manifesto launch, which was due to take place today, following the raid on the home of one of its Assembly members, Michael Copeland, by police last Friday as part of a money laundering investigation.
Mr Copeland has denied any wrongdoing.
Ulster Unionist strategists have chosen to have the manifesto launch on Wednesday.