The long-awaited final appeal of a Christian woman sentenced to death under Pakistan’s controversial blasphemy laws has been adjourned after a judge said he could not hear the case.

Justice Muhammad Iqbal Hameed-ur-Rehman, one of three judges who met amid heightened security in Islamabad to hear the appeal, said he could not rule on whether Asia Bibi’s 2010 conviction for insulting the prophet Muhammad should stand because of his involvement in a related case.

The supreme court judge said he had overseen the appeal hearing of Mumtaz Qadri who was convicted of murdering Salmaan Taseer, a leading liberal politician who had campaigned for Bibi to be released.

Bibi’s laywer, Saif-ul-Mulook, said it would probably take weeks or months for a replacement judge to be found and for the appeal to be rescheduled.

Bibi was accused of blasphemy after rowing with two Muslim women in her village in Punjab in 2009. The lawyer said the case against her was weak, not least because the testimony of the women was contradicted by other witnesses and did not meet the high standard of proof demanded by Islamic law.

Pakistan’s blasphemy laws have been criticised by human rights groups who say they are often used maliciously and to persecute religious minorities in the Muslim majority country.

The man who lodged the original complaint with police, Qari Muhammad Saalim, a village mullah, was in court for the hearing, along with a contingent of lawyers who offer their services for free in such blasphemy cases.

Ghulam Mustafa Chaudhry, the lead lawyer, who heads a group called the Movement for the Finality of the Prophethood, said Bibi had already been found guilty by two courts. “When they execute her it will stop other people from committing blasphemy,” he said.

Hardline religious groups have demanded the government carry out the death sentence, which has never happened in a blasphemy case before. In March, thousands of protesters held a protest outside parliament in which they demanded her execution.

This week, the Shuhuada Foundation, a group connected to Islamabad’s infamous Red Mosque where Islamists fought battles with security forces in 2007, warned that its supporters would take to the streets and become “a centre for the anti-government movement” if Bibi was released.

Despite the presence of riot police outside the supreme court there were no signs of any protesters on Thursday. Chaudhry said his group was “totally peaceful”.

“We are ready to accept the verdict of the court,” he said.

Jon Boone in Islamabad