Pakistan's supreme court Friday banned former prime minister Nawaz Sharif from participating in elections for life, as his embattled ruling party prepares for nationwide polls due later this year.

The ruling was the latest in a series of blows to Mr Sharif who was ousted from the premiership over graft allegations last July.

Supreme Court Justice Umar Ata Bandial described the ban on Mr Sharif as "permanent" in a judgement read to the court, clarifying the length of an earlier ruling that disqualified the former premier from office.

The decision was immediately panned by Mr Sharif's ruling Pakistan Muslim League-Nawaz party (PML-N).

"Today once again, the three-time elected prime minister of Pakistan has been disqualified for life," state minister and Sharif ally Marriyum Aurangzeb told reporters outside the court.

Last month, Nawaz's brother Shahbaz Sharif formally took charge of the PML-N after an earlier court ruling banned the former premier from heading the party.

The Sharifs and their supporters have repeatedly denied allegations of corruption, suggesting the former prime minister is the victim of a conspiracy driven by Pakistan's powerful military establishment.

Mr Sharif was the 15th prime minister in Pakistan's 70-year history - roughly half of it under military rule - to be removed before completing a full term.