The court dismissed his petition to review his death sentence, which was handed down in 1991. Mr Singh's lawyers at the time failed to appear for the hearing.
"The trial was conducted in English - Mr Singh does not speak or understand English - and an interpreter was not provided."
Ms Uppal says that his trail was fast tracked and that the main witness has repeatedly changed his version of events.
Mr Singh's hanging was most recently postponed in 2009 after Pakistan's Prime Minister, Yousuf Raza Gilani, intervened in the case.
In 2008, former Pakistani President Pervez Musharraf rejected his mercy petition and signed his death warrant.
"I believe that ultimately this man is being caught up in the political manoeuvrings of Delhi and Islamabad," Ms Uppal said.
"There is speculation that Pakistan wants the return of some of its prisoners held in India in exchange for the release of Sarabjit Singh.
"My aim is to make ordinary people aware of the terrible suffering - and the grievous miscarriage of justice - that this man has experienced."
