The 36-year-old Streatham MP said he believed Labour could win power in five years' time, adding: "I want to lead that effort as part of a really big Labour team, getting Labour back into office."
Umunna, the shadow business secretary, has been increasingly prominent in the Labour party despite only entering politics in 2008, and has been tipped as "Britain's first black prime minister."
Here are 12 things about the would-be party leader:
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