A coalition of conservative civic groups formally demanded Thursday that the Seoul city government hold a residents\' referendum to block a controversial project to provide free lunches to all elementary school students in Seoul, activists and officials said. The project of offering free school lunches, initiated by the main opposition Democratic Party (DP), has become a hot political issue since last year with opponents describing it as a \"populist\" campaign to win votes, while supporters say the ruling party should put its budget priority on welfare.