Former Pakistan prime minister Nawaz Sharif could be barred from contesting the upcoming general election, the country's attorney general Malik Qayyum said on Monday.

Sharif, who returned home on Sunday evening after a seven-year exile, had said he will file nominations for the January polls along with his wife Kulsoom and his brother Shahbaz Sharif in Lahore [Images] on Monday, the last day for submitting the apers.

Sharif had refused to say whether his party would boycott the elections, saying that the decision would be made by an alliance of opposition parties including his own.

"As the election law stands today, it is highly doubtful that Nawaz Sharif can contest elections," Qayyum told Dawn News televesion channel. "Sharif is likely to be barred because he had been sentenced to life imprisonment before he went into exile in 2000," he added.

The prison term was awarded to him following his conviction on charges of corruption and attempting to turn a plane that was carrying President Pervez Musharraf [Images] back to Pakistan from a foreign trip in 1999.

Musharraf, who was then the army chief, contacted army commanders on the ground and succeeded in carrying out a bloodless coup against Sharif in October 1999. The two men have been bitter rivals since then.