Critics say tough new secrecy laws coming into effect in Japan are draconian, with protesters calling for them to scrapped.

In 2009, investigative journalist Masakatsu Ota uncovered a top secret deal between Japan and United States that allowed nuclear weapons to be brought into Japan during the Cold War.

Ota said the reports were very much in the public interest.

"A key person in government confirmed it for the first time and the reports triggered an inquiry," he said.

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"The people got the truth and because they did, they could think more deeply about new policies and the nuclear issue. We have special feelings about this because of atomic bombing of Hiroshima and Nagasaki."

Under the new secrecy laws exposes like Ota's will be much harder to do.

Laws needed to 'tighten' national security

Whistleblowers who hand over state secrets can get up to 10 years' jail and journalists encouraging them can get five years in prison.

Experts have described the laws as extreme and part of prime minister Shinzo Abe's wider agenda to revise Japan's constitution.

Law Professor Lawrence Repeta from Tokyo's Meiji University said the government has a lot of power.

"They say the right to freedom of speech should only be respected when it doesn't disturb public order," he said.

"They also say that in their constitution they propose the government has authority to declare state of emergency and rule by cabinet."

Mr Abe said Japan needed the new laws to exchange military secrets like submarine technology with allies like Australia and to tighten the nation's security in times increasing regional tension.

'Democracy is regressing' in Japan

But the public does not agree.

The majority are against the laws and at protests across the country over the weekend people called for them to be scrapped.

One elderly woman told the ABC: "The people's right to know and freedom of press is disappearing. Democracy is regressing".

Another protester said Japan was heading back to its militarist past with these new laws.

"When Japan headed to militarism, people were arrested if they showed opposition, that's the scariest thing. Democracy has not matured yet, but it's been developing and I want to stop this move," the protester said.

Already the government is set to classify 500,000 documents as state secrets.

Critics have said the real danger of these laws will see the government ultimately deciding what is secret and the definitions can be vague.

From December 10, 19 government ministries can designate state secrets under 55 categories covering defence, diplomacy and security and they can stay secret for up to 60 years.