The senate body tasked with examining the amendment decided against it unanimously earlier this week, government senator Muhammad Javed Abbasi told AFP Thursday.
"According to Islamic traditions, it's understood that a girl becomes adult in between 12 to 16 years of age, so how can we define an age for marriage," Abbasi said.
Child marriage remains common in some areas of deeply conservative Pakistan, where woman have sought their rights for decades.
A previous attempt to amend the marriage bill last year was scuttled by a religious body which branded it "blasphemous" and against Islam.
The Council of Islamic Ideology said there was no specific age limit for marriage in sharia law as an individual can marry when he or she reaches puberty and puberty cannot be defined by age.
On Thursday human rights activists slammed the latest decision.
"Those who blocked this amendment should be ashamed of themselves," said activist Hina Jilani.
"Their interpretation is wrong," she said, adding that doctors clearly advise against the marriage of young girls for health reasons.
"We will confront this extremist and fundamentalist ideology and will launch protest," she said
