Islamabad: Pakistan's opposition parties on Thursday sought the immediate resignation of Prime Minister Yousuf Raza Gilani following his conviction by the Supreme Court for contempt on the issue of pursuing graft cases against President Asif Ali Zardari.

"In light of the verdict, I think Prime Minister Gilani should resign immediately rather than prolong the issue," Nawaz Sharif, chief of the main opposition party PML-N said.

The PML-N would no longer accept Gilani as the premier and the government was "on a wrong wicket" while the Supreme Court is "on high moral ground and people should back the truth", Sharif said.

Cricketer-turned-politician Imran Khan, chief of Pakistan Tehrik-e-Insaf took to social networking site Twitter to seek Gilani's resignation.

"After SC judgment PM has lost whatever shred of legal & moral authority he had," he tweeted.

Chief of the fundamentalist Jamaat-e-Islami party Munawar Hussain also urged the prime minister to quit as he had "lost moral ground" after the judgment.

"The prime minister should have himself declared by now that I am no more prime minister," he said.

"The Supreme Court sentenced him in an honourable manner and it also got its verdict implemented. He is now a convicted person and he cannot remain prime minister now," Hussain said.

Gilani was today convicted and given a symbolic sentence that lasted briefly.

The Supreme Court had been pushing the government to reopen cases of money laundering against President Zardari in Switzerland since December 2009, when it struck down a graft amnesty issued by former military ruler Pervez Musharraf.

The government has refused to act, saying the President enjoys immunity in Pakistan and abroad.