A Christmas message calling for prayers for those charged under Pakistan's blasphemy laws has led to death threats against the son of a provincial governor, who killed five years ago for criticising the same laws.

The case highlights the continuing influence in Pakistan of Muslim hardliners who praise violence in the name of defending Islam, despite a government vow to crack down on religious conservatism.

The hardliners called for mass protests if police do not charge activist Shaan Taseer with blasphemy against Islam, a crime punishable by death.

Taseer's father, Punjab governor Salman Taseer, was shot by his bodyguard for championing the case of a Christian woman, Asia Bibi, who was sentenced to death under the blasphemy laws.

He had been advocating reforms in the blasphemy laws that are used to mostly harass minority groups.

READ MORE: Living in fear under Pakistan's blasphemy law

In a video message posted on his Facebook page, Taseer, a Muslim, is seen wishing a happy holiday to Christians, and also asking for prayers for the woman and others victimised by what he called "inhumane" blasphemy laws.

Taseer said on Monday that he had received "very credible death threats" from supporters of the hardline Muslim philosophy that inspired his father's killer, bodyguard Mumtaz Qadri.

"They are sending me Mumtaz Qadri's photos with messages that there are several Mumtaz Qadris waiting for me," he told Reuters news agency late on Monday.

Shahbaz Taseer, the other son of Salman Taseer, was freed last year after five years in captivity.

Hardline groups

Tens of thousands people attended Qadri's funeral last March after he was hanged for killing the governor because they considered him a hero, highlighting the potential for this case to become another flashpoint.

More than 200 people in Pakistan were charged under blasphemy laws in 2015 - many of them minorities such as Christians, who make up one percent of the population.

Critics say the laws are often used to settle personal scores, and pressure for convictions is often applied on police and courts from religious groups and lawyers dedicated to pushing the harshest blasphemy punishments.

At least 65 people, including lawyers, defendants and judges, have been murdered over blasphemy allegations since 1990, according to figures from the think-tank Center for Research and Security Studies and local media.

A spokesman for the hardline group, Sunni Tehreek, said it was demanding police in Lahore to charge Shaan Taseer with blasphemy against Islam.

Police declined to comment and a copy of the police report on the complaint did not mention Shaan Taseer by name.

The police report did reference the Christmas message and opened an investigation under the blasphemy laws' Section 295-A, which bans hate speech against any religion.

However, Sunni Tehreek has threatened mass street protests unless the younger Taseer is charged under Section 295-C, blasphemy against Islam or the Prophet Muhammad.

Provincial Punjab government officials could not be reached for comment.