The ruling meant that Zia will remain in jail awaiting trial in a corruption case involving shipping contracts.


Zia is accused of misusing her power while awarding two contracts to a local company, Global Agro Trade Company, when she was in office in 2003.


The contracts involve receiving shipments of containers carrying goods into Bangladeshi ports.


Zia has insisted she is innocent, saying the corruption charges were a conspiracy to tarnish the image of her family and party.


Zia's main rival, another former prime minister, Sheikh Hasina, has been held since July on extortion charges.


Bangladesh, an impoverished nation of 145 million people, has been labelled as one of the world's most corrupt countries by Berlin-based anti-corruption watchdog Transparency International.


The country's military-backed interim government says it is fighting corruption, and will improve electoral rules and clean up the nation's violent factional politics before holding new elections next year.