All lawmakers belonging to the Pakistan Tehreek-e-Insaf (PTI) party will resign from the National Assembly ahead of the voting to elect a new prime minister, Imran Khan's close aide Fawad Chaudhry said on Monday.

Chaudhry, the former information minister, said that the decision was taken in a meeting of the lawmakers of the party ahead of prime minister's elections for which the party has nominated ex-foreign minister Shah Mehmood Qureshi.

"Pakistan Tehreek-e-Insaf (PTI) Parliamentary Committee has decided to resign from the National Assembly. Today, all members of the Assembly are submitting their resignations to the Speaker," Chaudhry tweeted.

He also announced that the former ruling party will fight for freedom and not become part of any government which was being formed under a "foreign agenda” – a reference to an allegation by Imran Khan that the US was involved in a conspiracy to topple his government. ?

The decision came as Pakistan parliament was set to meet to elect the new prime minister in the wake of ouster of Imran Khan through a no-trust motion.

Opposition candidate and Pakistan Muslim League-Nawaz (PML-N) president Shehbaz Sharif and former foreign minister Shah Mahmood Qureshi are in the race to become the new premier.?

The National Assembly has been summoned to meet at 2:00 PM (local time) for the crucial vote, according to its Secretariat.

Qureshi apparently has little chance to succeed as his party has been depleted by the defections.

In the house of 342, the winning candidate should get support of at least 172 lawmakers. The combined opposition that is supporting Shehbaz has shown the requisite numbers in the no-trust vote.

Meanwhile, GEO TV quoted sources as saying that Imran Khan has decided to quit as a member of the National Assembly.

"We will not sit in this Assembly under any circumstances," sources privy to the matter quoted Khan as saying.

He said that PTI will not sit in the Assembly with the people who have robbed Pakistan and who have been "imported by foreign forces".

"We have made this decision to keep the institutions under pressure who want this government to run the country [...] we will not let them continue."

However, sources said that most of the party members opposed Khan's decision to tender resignations, and instead, advised that they should face the Opposition strongly at every front.

Khan responded, saying "I will resign even if I am left alone."

The process of electing the new leader of the house began on Sunday after Khan was removed from office through a no-confidence vote, becoming the first premier in the country's history to be sent home after losing the trust of the House.?

Earlier, Khan's party discussed the issue of mass resignation in its Core Committee meeting on Sunday but it failed to reach any decision.

Chaudhry told the media after the meeting that PTI lawmakers would resign if Shehbaz was allowed to contest for the post of prime minister. But the decision was left for the PTI parliamentary group which met ahead of the assembly session.

Ahead of the election of the new prime minister, the opposition parties were holding talks to finalize the new cabinet as well as agree on the names of the speaker and deputy speaker.?