ISLAMABAD: Pakistan's parliament will on Thursday begin a debate of no-confidence in the leadership of Prime Minister Imran Khan, which could see the former cricket star ousted and the return of political uncertainty in the nuclear-armed country.

Khan, 69, has been facing mounting criticism of his performance, including his management of an economy beset by high inflation and rising deficits, and he lost his majority in parliament on Wednesday when a main ally quit his coalition.

"The prime minister is as good as gone," the influential English-language Dawn newspaper said in an editorial on the front page of its website.

Parliament will begin debate on Khan's leadership at 4 p.m. (1100 GMT). A vote on the motion must be held by Monday.

On Wednesday, Khan's main parliamentary ally, the Muttahida Qaumi Movement (MQM), abandoned his coalition and threw its lot in with the opposition seeking to oust him. 

Opposition leaders had called on Khan to resign even before he lost his majority in parliament, but his aides have said he will not quit.

Khan's ouster could mean another round of instability in a country in which the military has a long record of intervening in politics and no prime minister has ever completed a full five-year term.

Political analysts said Khan enjoyed the support of the military when he won an election to become prime minister in 2018 but he later lost the generals' favour over various wrangles.

Khan has denied ever having the backing of the military and the military, which has ruled Pakistan for about half its history, denies involvement in civilian politics.