Pakistan's Supreme Court charged the embattled prime minister with contempt of court on Monday for his refusal to re-open old corruption cases against President Asif Ali Zardari, complicating the country's political crisis.

Prime Minister Yusuf Raza Gilani has said that if he was convicted he would be forced to step down. He could also face up to six months in jail.

However, the case - which has raised tension between Pakistan's civilian leaders and the Supreme Court - is expected to drag on and paralyse decision-making.

You, Syed Yusuf Raza Gilani, have willfully disobeyed the direction of this court, said Justice Nasir-ul-Mulk, the head of the seven-judge bench hearing the case. Thereby you have committed contempt of court ... and you are to be tried.

The judge asked for a plea and Gilani answered that he was not guilty.

Proceedings will start on February 16 when the prosecution will submit its evidence.

The hearing lasted less than half an hour and Gilani left soon after, waving confidently to crowds of lawyers huddled under gloomy grey skies and a persistent drizzle. The black-suited lawyers divided themselves into two factions, chanting support for either the government or the Supreme Court.

The civilian-judicial confrontation stems from thousands of old corruption cases thrown out in 2007 by an amnesty law passed under former military president Pervez Musharraf.

Zardari is its most prominent beneficiary and the main target of the court, which voided the law in 2009 and ordered the re-opening of cases accusing the president of money laundering using Swiss bank accounts.

Gilani and his advisers have refused to ask the Swiss to reopen the cases, citing the president's constitutional immunity as head of state. The prime minister had appealed against the court's decision to charge him with contempt, but that appeal was dismissed, paving the way for Monday's indictment.

The prime minister's actions reek of protecting the president over our system of democracy, the Express Tribune newspaper said in an editorial.

Even if the president's immunity is upheld, it will no longer be applicable once he is out of office and in that eventuality there may be no legal or constitutional hitch in preventing the Supreme Court from going ahead on this issue.

That is the view held by many other commentators, who hail the Supreme Court's actions as a badly needed advance for the rule of law and accountability in Pakistan, where corruption tops the list of opinion polls as the country's biggest problem.

Others say the Supreme Court's pursuit of Zardari and his Pakistan People's Party (PPP) is bad for democracy and strengthens the hand of the powerful military, which has staged three coups since 1947 and ruled the country for more than half of its history.

At one level, this serves the army's purposes, said Najim Sethi, editor of the weekly Friday Times. They want the politicians to fight amongst themselves and remain discredited.

The constant infighting allows the army to solidify its control over foreign policy and national security, and limits the civilian government's attempts to control the military.

This will not be good news for democracy, said political analyst Hasan Askari Rizvi. Once again, non-elected institutions are trying to re-formulate the elected institutions. Previously the military was doing it, now it is the judiciary.

Political instability and brinksmanship often distract Pakistani leaders from a staggering number of challenges, from a Taliban insurgency to rampant poverty.

The performance of the government is already poor and now the attention of the government is fully diverted to survival, said Rizvi. So survival becomes the key issue and other issues are on the sidelines.

(Additional reporting by Serena Chaudhry and Rebecca Conway; Writing by Chris Allbritton; Editing by Serena Chaudhry and John Chalmers)