A new bill in Mauritania making slavery punishable by up to 10 years in prison is inadequate, says a lobbying group.
Many Mauritanians are born into slavery
Anti-Slavery International welcomed the Mauritanian government's initiative but said the proposed law was too weak.
Slavery has existed for centuries in Mauritania. A presidential decree abolished it in 1981, but no criminal laws were passed to enforce the ban.
This meant slavery continues as before and a huge effort is still needed to eradicate the practice, the group says.
"Unfortunately the proposed bill only defines an element of the practice in Mauritania," spokeswoman Romana Kacchioli told the BBC Network Africa programme
It does not cover contemporary aspects of slavery, such as forced marriage, indentured labour or debt bondage, she said.
"The bill so far is rather weak."
She said they and Mauritanian campaign group SOS Slavery were lobbying the government to strengthen the definition.
Any new legislation should punish slavery by up to 30 years in prison and provide for reparation payments to the victims, she said.
Mauritania's newly elected President Sidi Ould Cheikh Abdallahi promised to "permanently" eradicate slavery during his campaign.