Release International has called on Pakistan to repeal its controversial blasphemy laws as hundreds remain in prison on dubious charges.

The call comes half a year after Christian woman Asia Bibi fled to Canada with her family following her release from death row for blasphemy. 

The US Commission on International Religious Freedom (USCIRF) recently reported that some 80 people remain imprisoned in Pakistan on blasphemy charges. 

In its latest 'Freedom of Thought' report, the USCIRF calls Pakistan a "perennial offender" in imprisoning people on blasphemy charges. 

It highlights the case of Sawin Masih, a Christian road sweeper arrested in 2013 for blasphemy after being accused of insulting Islam during a private conversation with a Muslim friend. 

The accusation was broadcast by the local mosque over its loudspeakers and over 3,000 people then attacked Masih's home, while also looting and vandalising numerous other Christian homes, shops and churches in the area, USCIRF reports.

Hundreds of Christian families were displaced as a result of the violence and Masih was sentenced to death in March 2014.  He remains in prison more than five years later. 

"The authorities prosecuted a total of 1,170 blasphemy cases between 1987 and 2012, with scores of new cases every year," USCIRF says.

"Civil society reports estimate that in 2017 alone at least 50 individuals were imprisoned on charges of blasphemy, with at least 17 facing possible death sentences."

In a 2018 report, Amnesty International said there had been a large increase in blasphemy cases since the 1980s, with hundreds of people from different faiths being affected. 

"A total of 633 Muslims, 494 Ahmadis, 187 Christians and 21 Hindus have been accused under various provisions on offences related to religion since 1987," its report said. 

However, Release partners fear that the actual number of Christians imprisoned on blasphemy charges could be far higher.

"Given that Christians make up just two per cent of the population, the numbers charged are disproportionately high," said Paul Robinson, Release International CEO.

"Christians are ten times more likely to be accused of religious offences in Pakistan."

He condemned the blasphemy laws as "weapons of religious discrimination" as he called on the Pakistani government to repeal them. 

"The blasphemy laws have been used to make false allegations against Christians, often to settle scores. Just to accuse someone of blasphemy can light a fuse that leads to murder," he said.

"The blasphemy laws are weapons of religious discrimination. They must be repealed."