The presidential order summoning the special session at 5.30pm on Friday came a day after a three-judge bench, headed by Chief Justice Iftikhar Mohammad Chaudhry, disqualified Mr Gilani as prime minister and member of the lower house on the ground of an earlier contempt-of-court conviction, plunging the country into political uncertainty.

The National Assembly secretariat also issued a schedule for the prime ministerial election, which the Pakistan People’s Party and its coalition allies seem to sure to win against a likely opposition candidate because of their overwhelming majority in the 342-seat house.

The schedule requires nomination of the candidates to be delivered to the National Assembly secretary by 2pm on Thursday, their scrutiny by the house speaker an hour later and an open voting to be recorded on Friday from 5.30pm onwards through a parliamentary process of division.

While a meeting of the PPP’s parliamentary group on Wednesday authorised President Zardari, as party co-chairman, to name the party candidate, speculation has already begun about the fate of a successor if a legal controversy that led to Mr Gilani’s dismissal is raised again in the Supreme Court before the five-year term of the present National Assembly runs out in March 2013.

Mr Gilani was convicted in April and sentenced to a symbolic “imprisonment till the rising of the court” lasting about 30 seconds for following a party directive against writing to Swiss authorities -- as directed by an earlier court order -- to reopen disputed money laundering charges against Mr Zardari on the grounds of a presidential immunity.

The PPP insists it will not allow what it calls “the trial of the grave” of its assassinated leader Benazir Bhutto, who was the main accused in the charges brought in the 1990s by the then government of Pakistan Muslim League-N, now the main opposition party in parliament which wants the controversial charges to be reopened.

Tuesday’s court order, which overruled a ruling of National Assembly Speaker Fehmida Mirza sparing Mr Gilani the mischief of disqualification due to his April 24 conviction, came as a bombshell against the government just five days after the National Assembly in effect gave the prime minister a fresh vote of confidence by passing his fifth budget and adopted a resolution endorsing the speaker’s May 25 ruling as one which “cannot be questioned”.

The first dismissal of a prime minister by a court order in Pakistan’s history left the country without a federal cabinet, forcing President Zardari, who had already been divested of executive powers under the Eighteenth Amendment of the Constitution in 2010, to cancel a visit to Russia that would have begun on Wednesday, and that vacuum will continue until a new prime minister takes office after Friday’s vote.