A Japanese "cowboy" and self-proclaimed leader of the Fukushima nuclear resistance movement is refusing to leave his beloved cattle and the land of his forefathers despite government orders.

Masami Yoshizawa is also resisting government attempts to have his herd slaughtered, saying the beasts should be studied to better understand the health effects of long-term radiation exposure.

Mr Yoshizawa's property is just 14 kilometres from the shattered reactors at the Fukushima nuclear plant and his cattle have already been found to be contaminated with elevated levels of radioactive caesium.

Some of them have even developed white spots.

Scientist have descended on his property, saying it is important his herd is studied.

The ministry of agriculture has begun an investigation, but so far everyone is baffled.

"I showed these spots to many vets who came to my farm. But none of them knows what they are. I think it's the result of radiation," Mr Yoshizawa said.

Mr Yoshizawa's fight to stay on his land and to keep his cattle alive has been the subject of debate in Tokyo, with his case raised in the national parliament.

"I am violating the law. But I won't obey what the government says, because we were betrayed. Our community was destroyed by the nuclear disaster," he said.

"Instead of slaughtering them, these cattle should be used to study the long-term effects of radiation. Killing them is destroying evidence.

"I am a cowboy, and cowboys do not abandon their cows. I will stay with them until I die."