Pakistan's Supreme Court has declared Prime Minister Yusuf Raza Gilani ineligible for office after the premier was convicted of contempt.

The Supreme Court on 26 April convicted Gilani for refusing to ask Swiss authorities to reopen corruption cases against President Asif Ali Zardari in a highly politicised case.

Both are members of the ruling Pakistan People's Party.

Under the constitution, anyone convicted of defaming or ridiculing the judiciary is barred from being an MP.

The matter fell first to the speaker of parliament, also a member of the main ruling Pakistan People's Party, who on 24 May announced that there was "no question of disqualification".

Gilani subsequently decided not to appeal his conviction in a move interpreted as an effort not to antagonise the court into disqualifying him.

But today, the Supreme Court did so anyway.

"Yousuf Raza Gilani is disqualified from membership of parliament from April 26, the date of his conviction. He has also ceased to be the prime minister of Pakistan," said chief justice Iftikhar Muhammad Chaudhry, reading the order.

"The Election Commission shall issue a notice of disqualification and the president is required to take necessary steps to ensure continuation of democratic process," he added.