Speaking to the Westfälischer Anzeiger, 83-year-old retired engineer Hermann Schollmeyer apparently decided it was time to come clean, three decades after the incident he describes.

The official story had always been that radioactive waste was unintentionally leaked into the air at the THTR reactor in Hamm in May 1986, the western German newspaper reports.

But Schollmeyer now claims that the plant used the cover of the Chernobyl – which had released a cloud of radioactive waste over western Europe – to pump their own waste into the atmosphere, believing no one would notice.

“It was done intentionally,” Schollmeyer said. “We had problems at the plant and I was present at a few of the meetings.”

The problems related to balls of radioactive fuel getting stuck in the plant's pipework.

“Some clever dick suggested we clean out the pipework by pumping helium through it. He thought that no one would notice because of the Chernobyl cloud.”

Although he admitted that he was not at the meeting at which the decision was made, Schollmeyer insisted there was no other explanation.

The engineer said though that he stood by the reactor’s safety record.

“There was never a failure at the plant,” he said. “I still have a really positive opinion about the reactor. We should have just been patient. We’d already ordered a filter system. But they didn’t want to keep the reactor shut down for another two or three weeks.”

When asked why it took him so long to come forward about the incident, the engineer said “no one asked me before.”

Hubertus Zdebel, a member of parliament for the Left Party, told Neues Deutschland that “if Dr. Schollmeyer’s account is accurate we are talking about a scandalous and criminal action.”