A prominent Islamic scholar has launched a blistering attack on Pakistan's blasphemy laws, warning that failure to repeal them will only strengthen religious extremists and their violent followers.

"The blasphemy laws have no justification in Islam. These ulema [council of clerics] are just telling lies to the people," said Javed Ahmad Ghamidi, a reformist scholar and popular television preacher.

"But they have become stronger, because they have street power behind them, and the liberal forces are weak and divided. If it continues like this it could result in the destruction of Pakistan."

Ghamidi, 59, is the only religious scholar to publicly oppose the blasphemy laws since the assassination of the Punjab governor, Salmaan Taseer, on 4 January. He speaks out at considerable personal risk.

Ghamidi spoke to the Guardian from Malaysia, where he fled with his wife and daughters last year after police foiled a plot to bomb their Lahore home. "It became impossible to live there," he said.

Their fears were well founded: within months Taliban gunmen assassinated Dr Farooq Khan, a Ghamidi ally also famous for speaking out, at his clinic in the north-western city of Mardan.

The scholar's troubles highlight the shrinking space for debate in Pakistan, where Taseer's death has emboldened the religious right, prompting mass street rallies in favour of his killer, Mumtaz Qadri.

Liberal voices have been marginalised; many fear to speak out. Mainstream political parties have crumbled, led by the ruling Pakistan People's party, which declared it will never amend the blasphemy law.

Sherry Rehman, a PPP parliamentarian who proposed changes to the legislation, was herself charged with blasphemy this week. Since Taseer's death she has been confined to her Karachi home after numerous death threats, some issued publicly by clerics.

Although other Islamic scholars share Ghamidi's views on blasphemy, none dared air them so forcefully. "Ghamidi is a voice of reason in a babble of noises seemingly dedicated to irrationality," said Ayaz Amir, an opposition politician and opinion columnist.

Ghamidi's voice stands out because he attacks the blasphemy law on religious grounds. While secular critics say it is abused to persecute minorities and settle scores, Ghamidi says it has no foundation in either the Qur'an or the Hadith – the sayings of the prophet Muhammad. "Nothing in Islam supports this law," he said.

Ghamidi deserted the country's largest religious political party, Jamaat-e-Islami, to set up his own school of religious teaching. He came to public attention through a series of television shows on major channels. They were cancelled due to opposition from the mullahs, he said. "They told the channels there would be demonstrations if I wasn't taken off air."

Three years ago gunmen fired a pistol into the mouth of the editor of Ghamidi's magazine; last year the police foiled a plot to bomb his home and school. Now the school is closed.

The core problem, Ghamidi said, was the alliance between Pakistan's "establishment" – code for the military – and Islamist extremists it uses to fight in Kashmir and Afghanistan. "They are closely allied," he said.

The blasphemy debate has exposed painful rifts in Pakistani society. One Ghamidi follower said his father, a British-educated engineer, called him an infidel for attacking the controversial law. "Our society is tearing itself apart," he said.

Tariq Dhamial, a lawyer representing Mumtaz Qadri, said more than 800 lawyers had offered to represent the self-confessed killer. "Everyone is behind Qadri. Doctors, teachers, labourers, even police – they believe he did the right thing," Dhamial said.Dhamial said the police intended to hold Qadri's trial in jail but the lawyers wanted it heard in open court. The latest hearing is due next Tuesday.

Even when out of Pakistan, Ghamidi features on television shows by phone, often outwitting extremist clerics with his deep knowledge of the Qur'an. But he eschews terms such as "liberal".

"I am neither Islamist nor secular. I am a Muslim and a democrat," he said. But even allies question whether religious argument alone can win the sulphurous blasphemy debate.

"When you talk about religion, you only provoke the forces of reaction who become more intolerant. Then governments become frightened and retreat,"

said Amir. "Ghamidi's is a voice for the converted. But that won't solve our problem."

• This article was amended on 21 January 2011. The original referred to Jamaat-e-Islami as Pakistan's largest religious political party. This has been corrected.