Nawaz Sharif is serving a seven-year prison term at the Kot Lakhpat Jail in Lahore. (File)

Pakistan Muslim League-Nawaz leader Maryam Nawaz has released a video clip purportedly showing an accountability court judge allegedly confessing that he was "blackmailed and forced" to convict former premier Nawaz Sharif in a corruption case.

Addressing a press conference in Lahore on Saturday alongside the top leadership of the PML-N, Maryam Nawaz, the daughter of 69-year-old Sharif, said that her father's entire judicial process was severely compromised.

Nawaz Sharif is serving a seven-year prison term at the Kot Lakhpat Jail in Lahore since December 24, 2018 when the accountability court convicted him in the Al-Azizia Steel Mills case - one of the three corruption cases filed in the wake of the top court's July 28, 2017 order in Panama Papers case.

Nawaz Sharif and his family have denied any wrongdoing and allege that the corruption cases against them were politically motivated.

Maryam claimed Accountability Court Islamabad Judge Arshad Malik, who sentenced Sharif to a seven-year imprisonment in the Al-Azizia corruption case, confessed in his conversation with PML-N supporter Nasir Butt that he was "blackmailed and forced (by hidden forces)" to give verdict against the former premier.

The video purportedly shows the judge speaking to Butt and claiming that he was coerced to hand down the prison sentence against Sharif despite there being no proof of corruption against him.

The Imran Khan government termed the leaked video "doctored" and demanded its forensic audit, saying that "it is an attack on the judiciary."

Maryam said this was a "divine help" as her father failed to get justice in cases against him.

She said Judge Malik had categorically declared that there was no evidence of money laundering, commission or any other wrong financial transaction against Nawaz Sharif but he had "orders to send him jail for which I am repenting."

The judge was "blackmailed" into handing down the sentence against Sharif after some people threatened that they would release a private video of his, she alleged. She said the judge did not write the sentence but "was made to write" the prison sentence for Sharif.

She claimed the judge was under immense pressure to send the former prime minister to jail, and that he had contemplated committing suicide several times since.

Maryam said after the revelation of the video her father should not be kept behind the bars any more. She also hinted to use this video in the bail case of Sharif in Islamabad High Court.