The opposition alliance of GroenLinks-PvdA added more than 10,000 members in 2024, while other mainstream parties declined.

GroenLinks’ numbers grew by 14.5% to 46,508, on top of a 20% growth in 2023, while the number of Labour (PvdA) members grew by 9.6% to 47,869.

Groningen University, which records party numbers through its specialist documentation centre DNPP, said a dual membership campaign linked to the parties’ election alliance was partly responsible.

The two parties are still formally separate entities, but in the November 2023 general election they ran a joint list headed by Frans Timmermans and discussions about a merger are ongoing.

“It is not known how many members this involves, but if they merge into one party then obviously these dual memberships will disappear,” the university commented.

Three of the four coalition parties saw their membership numbers drop, while the animal rights party PvdD overtook the Socialist party (SP) to become the fourth largest party by membership.

Coalition parties shrinking

The right-wing liberal VVD shrunk by 7% to 20,902, while the farmers’ party BBB dropped 2.9% to 13,041 and Pieter Omtzigt’s NSC, founded in August 2023, was down 9.3% to 7,991.

The largest coalition party by vote share, the PVV, remained stable on one member, Geert Wilders, who has not allowed anybody else to join his party since it was founded as Groep Wilders in 2004.

The PvdD has 31,648 members, 4.3% more than in 2024, while the SP dropped below 30,000 to 28,737. In between them, the hardline Protestant SGP increased its numbers by 0.9% to 30,573. All three have more members than the more established VVD, D66 and the Christian Democrats (CDA).

Total membership of political parties increased marginally by 0.5% to 393,066, but the GroenLinks-PvdA dual membership campaign is likely to have affected the trend.

The far-right Forum voor Democratie remains the largest party in the Netherlands, but its membership fell for the first time in its 10-year history to 60,163, a 2.4% decline.

Forum has three MPs and won just under 233,000 votes at the last election, giving it a ratio of members to voters of less than one in four – far smaller than any other political party in the Netherlands. At the other end of the scale, the PVV had a ratio of one member per 2.45 million voters.