Tensions soon developed in the parliamentary party over Corbyn's leadership. Following the referendum on EU membership more than two dozen members of the Shadow Cabinet resigned in late June 2016, and a no-confidence vote was supported by 172 MPs against 40 supporting Corbyn. On 11 July 2016 an official leadership election was called as Angela Eagle launched a challenge against Corbyn. She was soon joined by rival challenger Owen Smith, prompting Eagle to withdraw on 19 July 2016 in order to ensure there was only one challenger on the ballot. On 24 September 2016 Corbyn retained leadership of the party with an increased share of the vote. By the end of the contest Labour's membership had grown to more than 500,000, making it the largest political party in terms of membership in Western Europe.