Race relations campaigner Lee Jasper has been selected as Respect's candidate for the Croydon North by-election.
Mr Jasper, who was policy adviser to Ken Livingstone when he was mayor, is currently chairman of the London Race and Criminal Justice Consortium.
He said: "I am delighted to be the Respect candidate.
"Following George's amazing victory in Bradford West I welcome the opportunity to offer the people of Croydon North a viable alternative to the tired and failed politics of the mainstream political parties.
"The responsibility for the economic crisis lies with banks and not the people of Croydon North and yet they are seeing their services cut and the welfare reforms are causing real hardship and acute distress."
Mr Jasper said his campaign will focus on speaking out for the poor, elderly and vulnerable and will highlight and challenge the austerity agenda.
He said: "There has to be a strong argument in defence of the unemployed and the working poor and in favour of creating jobs and opportunities.
"We need a fresh and dynamic approach to reducing crime, supporting the victims of the riots in their quest for compensation and tackling the strained relations between young people and the police."
Respect leader George Galloway described Mr Jasper as "the perfect candidate to fight this seat."
Mr Galloway said: "Lee has a stella track record in activism and community involvement.
"As well as being a crucial member of Ken Livingstone's team in governing London, as Director for Policing and Qualities. His record of public service in unequalled."
The Croydon North by-election follows the death of Labour MP Malcolm Wicks last month and is likely to take place on November 29.
The Conservatives have already selected Andy Stranack as their candidate and Marisha Ray will stand for the Liberal Democrats.
Labour will select its candidate from a shortlist of five this weekend.