The special court inside Rawalpindi's Adiala Jail, where Asghar is being held, rejected defence claims that the 65-year-old has mental health problems.
"Asghar claimed to be a prophet even inside the court. He confessed it in front of the judge," Javed Gul, a government prosecutor said.
"Asghar used to write it even on his visiting card."
Blasphemy is an extremely sensitive issue in Pakistan, where 97 per cent of the population is Muslim, and insulting the Prophet Mohammed can carry the death penalty.
But the country has had a de facto moratorium on civilian hangings since 2008.
Only one person has been executed since then - a soldier convicted by court martial.
In 2006, the then-president Pervez Musharraf commuted the death sentence on a British man convicted of murder after appeals from former UK prime minister Tony Blair and Prince Charles.