Dutch prosecutors said Thursday they want to drop charges against a father who isolated his children in a remote farmhouse because he is mentally unfit for trial.

Gerrit Jan van D., 68, was arrested in October 2019 for allegedly keeping his children in a room on his farm in the village of Ruinerwold for around 10 years.

But tests had found that a stroke in 2016 had left the former cult member partially paralysed, unable to speak and cognitively impaired, the prosecution service said.

"It is impossible that the suspect will be able to follow the criminal proceedings and participate," prosecutors said in a statement.

"This goes to the heart of a fair trial" and would violate the European Convention on Human Rights, they said.

A court will make a final decision on March 4, Dutch media said.

The public prosecution service said they understood the decision was "particularly hard" for the older children, who had helped investigators.

Gerrit Jan van D was arrested in October 2019 for allegedly keeping his children in a room on his farm for around 10 years
Gerrit Jan van D was arrested in October 2019 for allegedly keeping his children in a room on his farm for around 10 years ANP / Wilbert Bijzitter

Five of the children were found on the farm after a sixth, older brother walked into a local bar in a confused state and raised the alarm.

Van D. is also charged with sexually abusing two of his three older children who were not kept on the farm.

"In all their vulnerability, they have stated at length about terrible things they endured in their youth and young adulthood. About the way they grew up, the terrible secrets they carried with them and the consequences that this has for them to this day," the prosecution statement said.

Prosecutors said Van D. had isolated the children at the farmhouse from birth and beaten them from a young age to drive out "bad spirits".

One was tied up by his hands and feet as punishment while another was forced to spend an entire summer in a doghouse.

Van D. was charged with depriving the children of their liberty from 2007 to 2019 and punching them, kicking them and denying them food and drink.

Dutch media have said the family was "waiting for the end of time" as part of a doomsday cult.

An Austrian man identified as Joseph B., who was arrested at the same time has been freed on bail pending his trial.