Former NSC leader Nicolien van Vroonhoven has stood down as a candidate for the general election after being demoted from second place to fourth on the party’s list.

Van Vroonhoven originally said she would not be seeking re-election on October 29, but changed her mind after several MPs switched to other parties, notably Agnes Joseph, who defected to the farmers’ party BBB.

She was incensed at Joseph’s decision to keep her seat in parliament, having been elected on NSC’s list, a controversial practice known as zetelroof or “seat snatching”.

Van Vroonhoven was ranked second on the provisional list drawn up by the party leadership, behind leader Eddy van Hijum, but was pushed down to fourth when party members finalised the list at the weekend conference.

Opinion polls indicate that NSC, founded by Pieter Omtzigt two years ago, will struggle to hold on to any of its 20 seats in October after its support collapsed during its 11 months as a member of the right-wing coalition government.

Van Vroonhoven said the decision of members to promote caretaker home affairs minister Judith Uitermark and MP Merlien Welzijn above her was a “clear signal” that prompted her to step down.

“It has been a year of battles, defeats and disappointments,” she said. “I understand that the members see me as partially responsible for that, even though I hope that I and the rest of the team can find a way to get back up from it.”

As well as Joseph, MPs Diederik Boomsma and Aant Jelle Soepboer have quit parliament after joining the right-wing JA21 and the Frisian National Party respectively.

Foreign affairs minister Caspar Veldkamp also ruled himself out as a candidate after he resigned a week ago over the coalition’s policy on Israel, triggering the departure of the entire NSC group from the cabinet.

Van Vroonhoven will formally step down as parliamentary leader after Van Hijum, who was minister for social affairs until NSC quit the coalition, takes up Boosma’s seat this week.