A Pakistani court has barred President Asif Ali Zardari from pardoning a Christian woman sentenced to death on charges of insulting Islam, in a case that has prompted criticism over the country's blasphemy law.

Asia Bibi, a 45-year-old mother of four, requested a pardon from the president after a lower court sentenced her to death on 8 November in a case stemming from a village dispute.

The Lahore high court today barred Zardari from pardoning Bibi in a petition filed by Shahid Iqbal, a Pakistani citizen. Iqbal's lawyer Allah Bux Laghari told Reuters a pardon was illegal as the court was already hearing an appeal against her sentence.

"We believe it is the court's duty to evaluate the evidence against her, not individuals, and if she is found innocent, she should be freed," he said.

Human rights groups have demanded the repeal of the law, which they say discriminates against religious minorities who make up roughly 4% of Pakistan's 170 million-strong population.

A government minister said last week that an initial inquiry into the case of the Christian mother said she had not committed blasphemy but was falsely accused after a quarrel.

Blasphemy convictions are common although the death sentence has never been carried out. Most convictions are thrown out on appeal, but angry mobs have killed many people accused of blasphemy.