Japan is famously one of the planet’s safest countries. Crime has fallen for 13 straight years. The murder rate of 0.3 per 100,000 people is among the lowest in the world. The last major terrorist incident was more than two decades ago.

So the government’s claim that a proposed new law to punish people who plan to commit crimes has sounded a sinister note to some. Supporters say the conspiracy bill, which cleared the lower house this week, will protect Japan from the sort of terrorism that so horrifically visited Manchester on Monday.

The government is using the Manchester bombing to argue its case. Prime minister Shinzo Abe says it is his “responsibility” to ensure that counter-terrorism measures are in place ahead of the 2020 Tokyo Olympics and bring Japan into line with a UN treaty on global organised crime.

Opponents say the bill will allow police to stifle protests, launch more intrusive surveillance and trawl Facebook and other social media sites as they hunt for conspiracies. Takeshi Shina, a member of the opposition Democratic Party, insists it will do nothing to protect Japan from bombs but will damage the nation’s democracy.

“This bill takes Japan down a very dangerous path,” he says.

Such criticism was given extra weight this week by a terse intervention from the United Nations High Commissioner for Human Rights. In a letter to Abe, Joseph Cannataci, a UN special rapporteur, said the bill might “lead to undue restrictions to the rights to privacy and to freedom of expression.”

“In particular I am concerned by the risks of arbitrary application of this legislation given the vague definition of what would constitute the ‘planning’ and the ‘preparatory actions’ and given the inclusion of an overbroad range of crimes ... which are apparently unrelated to terrorism and organized crime,” he wrote.

‘Defective legislation’

The letter drew a testy response from Yoshihide Suga, the government’s chief cabinet secretary, who called it “clearly inappropriate”. Cannataci fired back, saying there was “absolutely no justification” to “push through seriously defective legislation in such a rush.”

Japan’s federation of bar associations says the police can use existing laws to investigate criminal conspiracies and questions why they should be given more powers. The nation’s liberal media has also come out against the bill. Given the nation’s militarist past, legislation giving the police greater authority touches raw nerves.

The LDP, which has dominated Japanese politics for six decades, has never wavered in its dislike of the nation’s 1947 constitution. Cobbled together by the victorious Americans in the humiliating aftermath of the second World War, the party believes the document, which issued ringing declarations of the inviolability of fundamental human rights, uprooted centuries of tradition.

An LDP draft constitution tosses out those imported concepts and replaces them with duties to the state. The national anthem and flag must be respected. Rights come with “responsibilities and obligations” and citizens “must comply with the public interest and public order”. Freedom of speech can be restricted if it interferes with this public order.

The prime minister would be empowered to declare a national emergency under “an extremely broad and undefined range of potential circumstances,” says one legal expert. Larry Repeta, a constitutional scholar, calls the document a blueprint for ending Japan’s post-war experiment in liberal democracy.

Media threats

Critics say the spirit of that draft increasingly animates government policy. A state secrets law in 2013 triggered protests from thousands of journalists, lawyers and scholars, to no effect. School textbooks have downplayed references to war crimes and increasingly toe the government line on Japan’s territorial disputes with its three closest neighbours: China, Russia and South Korea.

The government has also tried to muffle newspapers and television, earning another stinging UN rebuke last year. David Kaye, the Special Rapporteur on the Promotion and Protection of the Right to Freedom of Opinion and Expression warned last year of “serious threats” to the independence of the Japanese media.

Conservatives have led attacks on Kaye, saying he does not represent the UN. The response is similar to the first criticisms of Cannataci: justice minister Katsutoshi Kaneda said on Tuesday that special rapporteurs “conduct probes…in their capacity as individuals” and “do not reflect the UN’s position”.

None of this heat is likely to stop the bill’s final passage before mid-June. The Liberal Democrats (LDP) and like-minded parties control two-thirds of both houses. That lack of opposition, more than anything, should worry Japanese people, says Shina. There is not much point in having little crime, he says, if the state has the freedom to do what it wants.