* Gbowee accuses president of failing to fight corruption
* Liberia government says disagrees with criticism
MONROVIA, Oct 8 (Reuters) - Nobel prize-winning rights advocate Leymah Gbowee has quit her post in Liberian President Ellen Johnson-Sirleaf's government, criticising her fellow laureate for corruption and nepotism, her spokesman said on Monday.
Gbowee and Johnson-Sirleaf, Africa's first freely elected female head of state when she came to power in 2005, were named joint winners of the Nobel Peace Prize in 2011 for their work promoting peace in Liberia.
Gbowee, who helped Johnson-Sirleaf get reelected to a second term last year, is credited with helping to end Liberia's civil war by organising 'sex strikes' among the wives of fighters.
She had been serving as head of Liberia's Peace and Reconciliation Commission.
Omecee Johnson said that Gbowee resigned over concerns Johnson-Sirleaf had failed to root out corruption and nepotism in her government, but he declined to elaborate.
"Leymah Gbowee has resigned her post as head of the Peace and Reconciliation Commission, and the government of Liberia has accepted her resignation," Johnson told Reuters by telephone.
Liberia's government confirmed Gbowee's resignation and said it disagreed with her criticisms. Johnson-Sirleaf has three sons in top government posts but she has denied charges of nepotism and has said ending graft is a top priority.
Liberia is one of the world's poorest and least developed countries and is seeking to fund its recovery by drawing investment in its rich natural resources, which include vast iron ore deposits and offshore oil.
Rights advocates have expressed concern, however, that many of Liberia's resource deals are marred by fraud and do not provide the state with adequate revenue.
Global Witness said in September that Liberia's forestry department had given out a quarter of the nation's land to logging firms over the past two years in a flurry of shady deals.
(Reporting by Alphonso Toweh; Writing by Richard Valdmanis, editing by Diana Abdallah)
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Keywords: LIBERIA GBOWEE/