Pakistan's Supreme Court nullified on Wednesday the election last year of Punjab province's chief minister, a lawyer said, effectively dismissing Shahbaz Sharif and raising fears of renewed political instability.
The court also declined to rule on a challenge to an electoral ban on Punjab chief minister Shahbaz Sharif's brother, former prime minister Nawaz Sharif, effectively maintaining a bar on him standing for election.
The court's decisions to nullify the election of Shahbaz Sharif raises the prospect of confrontation between the country's two main political parties.
Pakistani stocks fell 4.2 per cent as investors sold on fears that the country was heading into a fresh phase of political instability.
'Shahbaz Sharif's membership (of the provincial assembly) has been cancelled,' Akram Sheikh, a lawyer supporting the Sharif brothers, told reporters outside the Supreme Court.
Neither of the Sharif brothers were in court.
Asked whether Shahbaz Sharif would remain chief minister of Punjab, Pakistan's biggest and politically most important province, Sheikh said: 'It's the natural consequence of this, how could he remain chief minister?'
Shahbaz Sharif vacated the CM House after the court's decision.
Both Sharif brothers were barred for legal reasons from standing in an election last year in which their party came second.
A court later acquitted Shahbaz Sharif over accusations of involvement in the extra-judicial killing of five militants in 1998, when he was the chief minister of Punjab, Pakistan's richest province and home to half its 160 million people.
That cleared the way for him to contest a by-election, which he won. He then became chief minister of Punjab.
Nawaz Sharif was ousted as prime minister in a 1999 coup by former army chief and president Pervez Musharraf.
He was barred from running in the general election in February last year because he had been convicted for the 1999 hijacking of then army chief Musharraf's aircraft, an action that triggered the military coup that overthrew him.
The Election Commission later ruled he could contest a by-election for a seat in the National Assembly. But in June last year, a court disqualified Nawaz Sharif from contesting the by-election.
The Supreme Court had been hearing challenges to that ruling.
The Sharifs head the Pakistan Muslim League (Nawaz) party, which came second in a general election in February last year.
The party later dropped out of a coalition with the party of former prime minister Benazir Bhutto, which won the most seats in the election, over a dispute over the restoration of judges Musharraf had earlier dismissed.
The brothers appear unlikely to ask the Supreme Court to review its decision. They have refused to appear before it in person and cast doubt on its legitimacy to hear the case.
Nawaz Sharif has already announced his support for a massive rally next month by lawyers whose protests over the past two years helped drive former President Pervez Musharraf from power.