ISLAMABAD: Pakistan’s president faced fresh calls to step down today after the Supreme Court struck down an amnesty that had protected the increasingly unpopular leader and several of his political allies from corruption charges.

The decision late Wednesday weakened the already shaky rule of President Asif Ali Zardari and sharpened political tensions in the nuclear-armed nation just as the United States and its other Western allies want it to unite and fight militants along the Afghan border.

While it is generally agreed that Zardari has immunity from prosecution as president, the court ruling means his opponents can now challenge his eligibility to hold the post. Zardari is already unpopular, in large part because of his close ties with Washington. The allegations of wrongdoing being heard in court will add to his troubles.

Zardari’s aides said any corruption charges against him were politically motivated and that there was no reason for him to step down. Critics countered he was morally obligated to resign, at least while the court heard any challenges to his rule.

The amnesty was part of a US-brokered deal with then-military ruler Pervez Musharraf that allowed former Prime Minister Benazir Bhutto to return home from self-exile and participate in politics without facing charges her party says were politically motivated.

Zardari, Bhutto’s husband, took control of the party after Bhutto was assassinated in 2007. Known as the National Reconciliation Ordinance, it stopped corruption investigations and probes into other alleged misdeeds or wiped away convictions in cases involving up to 8,000 ministers, bureaucrats or politicians from across the spectrum. Civil rights activists have criticised the amnesty as having unfairly protected the wealthy elite.

Zardari has been haunted by corruption allegations dating back to governments led in the 1990s by his late wife. He spent several years in prison under previous administrations. The Supreme Court this week heard allegations he misappropriated as much as $1.5 billion.

The court on Wednesday singled out an investigation that began in 2006 in a Swiss court into allegations of money laundering against Zardari and his late wife. Authorities in Switzerland suspended the case last year after the attorney general under Musharraf told them the government was no longer pursuing it. At the same time, Geneva authorities unblocked $60 million that had been frozen in Swiss bank accounts on request of Pakistani officials.

The court said this was illegal and ordered the government to ask Swiss authorities to reopen the case.

Switzerland Justice Ministry spokesman Folco Galli said it had not received any new request for international judicial assistance from the Pakistani government.

He said Pakistan must have an open criminal investigation into Zardari before it can file for Swiss help. If Zardari enjoys presidential immunity, there would be no legal basis for Switzerland to investigate accounts linked to him, he said.

Pakistani papers on Thursday welcomed the Supreme Court decision striking down the amnesty as a victory for justice. Many editorialists said it boded ill for Zardari.