Updated

A court ruled Thursday that President Asif Ali Zardari must relinquish his position as co-chairman of Pakistan's ruling party, a decision that could strip him of his main source of power and cause fresh political conflict in the country.

Zardari is facing other challenges in the courts to his rule, including old corruption charges he maintains are politically motivated. Since taking office in 2008, he has attracted a lot of criticism for his poor performance, but his loyalists say the judiciary — which has a history of meddling in politics — is out to get rid of him at any cost.

The Lahore High Court ruled on a petition filed 1-1/2 years ago by a lawyer who argued that Pakistan's constitution prohibits the president to simultaneously head a political party.

In its 35-page ruling, the court agreed, saying the president should perform his duties with "neutrality, impartiality and aloofness from any partisan/political interests." It went on to say the president must "dissociate himself from the political office" as quickly as possible.

Most other presidents in Pakistan have not been party leaders.

Farahnaz Ispahani, a spokeswoman for Zardari, who is currently in Russia on an official visit, said she had not seen the ruling and could not comment.

The president could choose to ignore the ruling or appeal it, which could stretch out the proceedings for many more months. His term ends in 2013.

Opposition party members urged him to step down immediately, according to local television reports.

Zardari became president not long after his wife, former Pakistani Prime Minster Benazir Bhutto, was assassinated in 2007. Pakistan has since been ravaged by Islamist violence. The West, which is helping prop up the government with billions of dollars in aid, would like to see political stability so it can concentrate on defeating militancy.

Last year, the parliament amended the constitution to reduce powers of the president that had been amassed by previous dictators, leaving the post as mostly ceremonial. But Zardari remained co-chairman of the Pakistan's Peoples Party, which is the largest in parliament.

Zardari's son, Bilawal Bhutto, holds the post of chairman, but does not live in Pakistan and as yet does not play much of a role in the day-to-day running of affairs.

Zardari's position as party co-chair means he wields significant influence over the government, which helps keep him in the job regardless of any popular anger against him. The head of the ruling party in Pakistan has immense powers of patronage at his disposal, ensuring he can keep his party loyal to him.

Furthermore, the prime minister is also a member of the party, so must obey Zardari.