Islamabad  - A Pakistani court on Monday ruled that former prime minister Nawaz Sharif was disqualified from contesting the upcoming by-elections because of his previous conviction, a spokesman from his Pakistan Muslim League-Nawaz (PML-N) party said.

"We reject the verdict because it is not based on the principles of justice. It is absolutely a political decision that has been dictated by a dictator," said Siddiqul Farooq.

Sharif is a staunch opponent of the embattled President and retired army general Pervez Musharraf, who ousted the former premier in a military coup in 1999.

He was convicted over a number of charges following the overthrow and exiled for more than seven years. His aids consider the conviction to be politically motivated.

Sharif returned a few weeks before February 18 elections in which his party emerged as the second largest party after inflicting a comprehensive defeat on Musharraf's political allies.

It supported Pakistan Peoples Party (PPP) of slain former premier Benazir Bhutto to form the new coalition government.

Sharif was previously barred from contesting the general elections.

He applied once again for contesting June 26 by-polls but was challenged in Lahore High Court.

A three member bench of the court ruled against him, prompting his angry supporters to chant slogans against Musharraf and what they called "his hand-picked judiciary."

The military-dictator-turned-civilian president deposed more than 60 independent-minded senior judges of the Supreme Court and four provincial High Courts under an emergency order on November 3.

They were replaced by his favorite justices, who approved his last year's controversial presidential election.

Sharif has advocated for the reinstatement of sacked judges. But the leading partner in new coalition government, the PPP, has been hesitant on the issue.

The former prime minister has been projected as the most popular political leader in Pakistan by a recent survey.

The opinion poll released last week by two Washington-based think- tanks, New America Foundation and Terror Free Tomorrow, showed that Sharif has seen a steady rise in his popularity, from 57 per cent favourable in the August 2007 poll, to 74 per cent in January 2008 and 86 per cent now.

If general elections were held today, Sharif's party would emerge as the clear winner, according to the survey. (dpa)