Pakistan's prime minister on Wednesday appealed against a court summons to face a contempt indictment next week, challenging an order that could ultimately force his weak government into early elections.

Pakistan's highest court on February 2 summoned Yousuf Raza Gilani to appear on February 13 to face indictment, impatient over the government's refusal to re-open corruption cases against President Asif Ali Zardari.

It was a shock move from the Supreme Court that sharply escalated pressure on the embattled prime minister a year before his government would become the first in the history of Pakistan to complete an elected term in office.

Gilani's lawyer Aitzaz Ahsan said he based the appeal on precedents set by top courts in Australia, Britain, France, India and the United States.

"My objection is that the court in its order on February 2 cited no specific reasons for initiating contempt of court proceedings against the prime minister," he told reporters.

Gilani had appeared before the Supreme Court on January 19, refusing to back down over citing Zardari's immunity as explanation for his refusal to obey the court's order to ask Switzerland to re-open corruption cases.

The Swiss shelved the cases in 2008, when Zardari took office.

If convicted of contempt, the prime minister could be jailed for up to six months and disqualified from public office.

Ahsan said there reasons not to indict the prime minister.

"The president enjoyed immunity and the Swiss authorities have also closed the case. I should not comment further on this issue," he said.

In order to hear the appeal, the Supreme Court will need to constitute a larger bench of nine judges -- not the seven who ordered him to appear.

A court official confirmed that the appeal had been received. Ahsan called for an early hearing, but no immediate date was announced.

Gilani had said last week that he would attend the February 13 summons and expressed opposition to conflict between state institutions.

Although Supreme Court Judge Nasir-ul-Mulk said there were grounds to proceed against Gilani, members of the government accuse judges of plotting with the army to wage a witch-hunt against the prime minister and president.

Legal experts say that Gilani can only avoid being charged by appealing, apologising or promising to write to the Swiss.

Ahsan, hugely respected by judges for his role in forcing the government to reinstate independent judges in March 2009, is considered Gilani's best hope of getting off the hook.

The allegations against Zardari were frozen by a Pakistani political amnesty imposed in 2007, which the courts overturned in late 2009.

Tainted by corruption allegations, Zardari is nicknamed "Mr 10 Percent" and spent 11 years in jail on charges ranging from corruption to murder, although his supporters point out that he was never convicted.

Zardari and his late wife, prime minister Benazir Bhutto, were suspected of using Swiss bank accounts to launder about $12 million in alleged bribes paid by companies seeking customs inspection contracts in Pakistan in the 1990s.

A Swiss prosecutor has since said it would be "impossible" to reopen the case against Zardari since he benefits from immunity as a head of state.