A Pakistani election tribunal disqualified a senior minister and ally of Prime Minister Nawaz Sharif on Monday for vote rigging in the 2013 election, a decision the opposition is likely to trumpet as vindication of its complaints.
Protests last year over cheating in the election, which brought Pakistan's first transition between civilian governments, were led by cricketer-turned-politician Imran Khan and raised fears about stability in the nuclear-armed country.
The tribunal disqualified Railways Minister Saad Rafique from his seat in the city of Lahore and called for a re-election within 60 days, setting the scene for a battle for votes between Sharif's party and Khan's.
Rafique denied irregularities, saying election organisers were responsible for any mistakes and he would challenge the ruling in the Supreme Court.
"The tribunal is punishing my party and my voters for the incompetence of the returning and presiding officers," Rafique told Reuters by telephone.
The judge overseeing the tribunal issued a one-page verdict disqualifying Rafique and calling for a by-election. Television channels reported that the judge castigated election workers and said ballot bags had been opened with a sharp object and records had been tampered with.
Sharif's Pakistan Muslim League, which denied any rigging, won the 2013 election with a sizeable majority while Khan, whose party came third, alleged widespread fraud. He organised a sit-in protest in central Islamabad to demand a new election.
The rally turned deadly in September when demonstrators clashed with police near government buildings and embassies and three people were killed.
The decision to unseat a close ally of the prime minister comes at a difficult time for Pakistan, already plagued by an Islamist insurgency, sectarian tension and recurrent power shortages, with many people deeply unhappy with the government's performance since it came to power.
Khan was not available for comment but his candidate who lost in the Lahore constituency in 2013 welcomed the ruling.
"It took us two years to get justice," the candidate, Hamid Khan, told reporters outside the court.
"A victory for the people of Pakistan," Khan's party said in a posting on Twitter.