But the timing of the resignation, the day before the local and European elections, raised questions - while she also did not pay the customary tributes to the prime minister, who had criticised her behaviour over expenses.
Home Secretary Jacqui Smith is understood to have told Mr Brown at Easter she wanted to stand down for her family - following expenses allegations against her. She said on Thursday he was the right man to lead the Labour Party.
For the Liberal Democrats, Danny Alexander told the BBC: "It is clear that the Labour government is in total meltdown, that Labour is finished as a government.
"The people of this country have clearly lost confidence in the Labour government and it seems now that ministers are losing confidence in their droves. We may well see more resignations."
He said it was "simply not possible to imagine" Labour continuing to govern for another year and called for a general election.
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