As her appeal approaches in October, Release International is calling for Bibi to be acquitted.
A farm labourer who was sentenced to death for blaspemy after a dispute with colleagues over bringing them "unclean" water, she has been on death row since 2009. Her family has been forced into hiding.
The appeal will be heard by Lahore's Supreme Court in Pakistan.
Release is calling for people to sign its petition to Pakistan Prime Minister Nawaz Sharif to abolish the "iniquitous" blasphemy laws.
More than 150,000 Christians have also signed a separate Call For Mercy petition pleading for her life.
Release International, which serves persecuted Christians around the world, called on the Prime Minister of Pakistan to repeal the blasphemy laws, which "are often invoked to take revenge, incite violent attacks and eliminate rivals," the charity said.
Chief executive Paul Robinson said: "We call on the government of Pakistan to abolish the blasphemy laws and seek to create a society where every Pakistani citizen is free to exercise their faith and live in peace with their neighbours."
Many others besides Bibi have been targeted by the blasphemy laws in Pakistan.
One cleric has offered 500,000 rupees – about £4,000 – for anyone who manges to murder Bibi, said Release.
Anglican leaders worldwide have also stepped up the pressure to save Bibi's life, Anglican Communion News Service (ACNS) reports.
Members of the recent Anglican Consultative Council meeting in Lusaka passed a resolution calling for her to be acquitted. Shunila Ruth, council member for Pakistan, who discussed the issue with the Archbishop of Canterbury when she visited London, told ACNS that Pakistan's blaspemy laws are "inhuman".