A senior member of party said they were trying to force PM Nawaz Sharif to step down.
The PTI party has 34 of the national assembly’s 342 seats, making it the second biggest opposition group.
Imran Khan has called for the prime ministers to step down, alleging vote rigging in the 2013 election that he won by a landslide.
Shah Mehmud Qureshi, a senior PTI leader, said the party would also withdraw from three out of four provincial assemblies in Pakistan.
The fourth province, Khyber Pakhtunkhwa, is under PTI control and officials there will not resign, he said.
The members of parliament’s resignations must be submitted to the national assembly speaker but correspondents said this would not happen on Monday as parliament had adjourned for the day.
Imran Khan, a former captain of Pakistan’s cricket team, has been demonstrating along with thousands of his supporters in the capital Islamabad since Friday to demand fresh elections.
His rally took place at the same time as a similar demonstration by anti-government cleric Tahirul Qadri, who told crowds that the protests must continue until they bring a “peaceful revolution”.
Nawaz Sharif’s victory was the first democratic transfer of power in Pakistan, which has a long history of coups.
Critics say Tahirul Qadri has close ties to Pakistan’s armed forces.
Supporters of Imran Khan and Tahirul Qadri are angry about Pakistan’s poorly performing economy, growing militancy, and the government’s failure to deliver services such as a steady electricity supply.
However, other opposition figures have criticized the demonstrations and Imran Khan’s call for people to stop paying tax bills in protest at the government.
Former president Asif Ali Zardari, co-chairman of the Pakistan People’s Party, the largest opposition party, said such “unconstitutional means” would not help the cause.
“Democracy will not be served by calls for civil disobedience nor by a stubborn refusal by any side to engage in a meaningful dialogue on political issues,” Asif ALi Zardari said in a statement.
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