Members of the PvdA and GroenLinks have voted overwhelmingly to back a joint campaign and manifesto ahead of the November general election, which will create a serious challenge to poll leaders VVD and the pro farmers BBB.

No fewer than 92% of Groenlinks and 88% of Labour voters voted in favour of the joint programme, which will see a single leader represent both parties.

After the results of the vote were made public, PvdA leader Attje Kuiken said she had not expected such a victory. “People want change,” she said. “Politics is currently about mistrust, about being against the other, but we have said ‘no, we will do it together’.”

GroenLinks leader Jesse Klaver said the joint group would not make empty promises to voters. “Perhaps things won’t get better for you at an individual level, but society at large will be a better place,” he said.

The PvdA and GroenLinks have nine and eight seats in the current parliament respectively. However, if the last poll of polls is to be believed, the combined group could take 20 to 26 seats.

However, the poll of polls dates from June, before the cabinet fell. A poll by Maurice de Hond this weekend puts the combined group on a par with the VVD and pro-farmers BBB at 25 seats each.

As yet it is unclear who will lead the combined ticket. As well as the two party leaders, EU the names of EU commissioner Frans Timmermans and Amsterdam’s PvdA chief Marjolein Moorman have been doing the rounds.

According to the De Hond poll, Timmermans could boost the joint party’s fortunes by a further three seats, making it potentially the biggest in parliament.

Broadcaster NOS says the establishment of a joint campaign and manifesto would appear to be the start of a full merger between the two groups.

GroenLinks itself is the result of a merger between four parties in 1990 while the PvdA was launched after World War II as a merger between three.