Political party membership in the Netherlands has reached a 40-year high, with 448,100 people currently members, according to research by Groningen University.

The total is up 57,000 on a year ago. Membership had been below 400,000 for decades. Political party membership helps determine how much subsidy parties receive from national government to support their operations.

The biggest party in terms of members is the far-right Forum voor Democratie, according to figures it supplied to the research team.

In terms of growth, GroenLinks added 16,258 members over the past year, taking its total to 62,000, while the PvdA has 64,000. The two parties are due to formally merge this year and will then become the biggest in terms of membership.

Fourth in the ranking is liberal democratic party D66.

The far-right PVV is the only party to have just one member – its founder Geert Wilders. Seven MPs for the PVV split off and set up their own operation earlier this year, partly because they were unhappy at Wilders’ refusal to introduce some form of party democracy.