Leading member of the Free Egyptians Party and MP Emad Gad resigned from the party on Monday despite the risk of losing his parliamentary seat as a result.
In December, Gad, who was deputy head of the liberal party, froze his membership over what he said was disagreement with the party's leadership. He handed in his notice earlier this week.
"I officially handed my resignation [Sunday] night," Gad said in TV comments late on Monday, saying the party's acting head Essam Khalil has accepted it.
Gad attributed his resignation to disagreement over the party's leadership and the way the party is operated.
"It's political life, not a business," he said without further explanation.
Gad said he no longer fully believes in "the party's mechanism, ideas, stances, and figures leading it," adding that the problem first arose after the election of the party's head and the head of the parliamentary bloc, Alaa Abed.
Under Egypt's constitution, MPs can be stripped of their membership if they change the capacity for which they were elected and if a two-thirds majority of the chamber votes on their removal.
This includes change of party affiliation or shifting from being a party member to an independent or vice versa.
Gad said that he supports such articles in the constitution, which he believes works towards a balanced representation in the chamber.
The vote is expected to take place once the parliament reconvenes next week, he said.
The Free Egyptians Party, founded in 2011 by business tycoon Naguib Sawiris, has seized the biggest party bloc in the new 596-member parliament, with 65 seats.
He stressed though that he has no problem with the party's "founders."
Prior to joining the liberal Free Egyptians Party over a year ago, Gad, a political analyst, was the secretary-general of the Social Democratic Party.