The Supreme Court convicted Gilani of contempt and subsequently disqualified him after he refused to revive graft cases in Switzerland against President Asif Ali Zardari, who heads the ruling Pakistan People's Party.
The apex court has also disqualified 11 federal and provincial lawmakers who have dual nationality and ruled that Interior Minister Rehman Malik, a close aide of Zardari, stands to lose his seat in Parliament as he had made a false declaration about his British citizenship at the time of the 2008 polls.
Gilani regretted that Parliament had failed to assert its rights.
"The Pakistani Parliament should have risen to the occasion when its boss (Prime Minister) was shown the door by the Supreme Court for protecting the Constitution," he said.
He said he was leaving the presidency, where he has been living since his disqualification, to go to the people as the general election would be held soon.
"I remained Prime Minister for about four-and-half years and stayed in the presidency for over three months and I thank President Zardari for that," he said.