A senator with the farmers’ party BBB has quit to become an independent member in what the leadership described as a “complete surprise”.

Eric Kemperman said he would stay in the Upper House and start his own party. He is also retaining his seat in the provincial assembly in Gelderland, where the BBB is the largest party in a five-way coalition.

The farrmers’ party remains the largest in the Senate with 15 members, one more than the left-wing GroenLinks-PvdA.

In a short statement on its website, the BBB said it regretted Kemperman’s decision, but it had no choice but to accept it. “The Senate party group and the provincial group in Gelderland will take on his work,” the statement said.

Senate group leader Ilona Lagas said she had “no idea” why Kemperman, 60, had decided to split from the party. “This was a complete surprise. The BBB is still waiting for an explanation,” she said.

Rik Loeters, leader of the famers’ party group in Gelderland, was equally bewildered after Kemperman announced his departure to party colleagues on Monday evening.

“He was the most critical voice when it came to compromises, but in a coalition you have to work together,” he said.

Lobby group row

Kemperman was at the centre of controversy last year when he was reported to have asked questions in the Senate that were drafted by a lobby group.

He said he had been helped by lawyers for Vastgoed Belang, an industry organisation representing private landlords, with dozens of questions about proposed rent controls.

The housing minister at the time, Hugo de Jonge, said the situation was “concerning” and members of parliament should represent voters rather than acting as “a go-between for the lobby of an interest group for real estate entrepreneurs.”