The Glasgow-based solicitor has been instructed by the family of Mohammad Asghar, who is from Edinburgh, to represent the former shopkeeper after he was arrested in 2010 in Rawalpindi, near the capital Islamabad, for claiming to be the prophet Muhammed, and convicted in January.
He was sectioned in the UK after being diagnosed with paranoid schizophrenia and four months after his release, following a month under observation in the Royal Victoria Hospital, he travelled to Pakistan.
Prime Minister David Cameron and First Minister Alex Salmond both condemned the sentence, which is being appealed by the charity Reprive in partnership with Mr Anwar.
Mr Anwar, Labour's shadow justice secretary Sadiq Khan and academics from the Muslim Institute and the Islamic Society of Britain are among those to have signed an open letter to Pakistan President Mamnoon Hussain and the Pakistani government appealing for clemency.
His supporters claim the case was really about a property dispute.
Mr Asghar became embroiled in the dispute with his tenant who brought the blasphemy complaint against him to police.
Mr Anwar said: "I will be working in partnership with Reprieve and lawyers in Pakistan to secure his release.
"His medical and mental health remains a source of serious concern and we hope that the judicial process can be accelerated to deal with this miscarriage of justice.
A spokesman for Reprieve said: "We look forward to ensuring Mr Asghar gets the help and support he needs."