In a bid to minimize the political damage from the latest pension system scandal, Chief Cabinet Secretary Yoshihide Suga on Tuesday admonished the government-affiliated Japan Pension Service and announced that a team will be set up to probe the massive theft of pension data.

The Japan Pension Service, which manages the basic national pension system designed to cover all residents in Japan, including foreigners who pay into the scheme, said Monday that part of its computer system was hacked and personal data on 1.25 million contributors and recipients was stolen.

Despite previous instructions not to open any suspicious email attachments, several JPS workers accessed a virus-infected file sent to their work computers.

Meanwhile, it was learned that about 550,000 of the 1.25 million cases were not protected by a password, a violation of an internal rule for JPS workers handling pension data, officials said.

The agency “should have responded to (the hacking) more seriously while doing their daily business operations,” Suga told a news conference. “(JPS) was overly optimistic about information security, and it should be held responsible for what was not done despite its internal rules.”

The leaked information included names, birthdates, addresses and pension ID numbers of individuals. JPS officials claim this information alone is unlikely to allow anyone to steal pension benefits.

But aides to Prime Minister Shinzo Abe are taking the data breach extremely seriously, probably because a public pension scandal in 2007 damaged his first Cabinet and contributed to his resignation as prime minister.

In 2007, millions of pension claims, then managed by the Social Insurance Agency, went missing, which subsequently enraged voters. Abe’s Liberal Democratic Party suffered a stunning defeat in that year’s Upper House election, which in turn helped aggravate Abe’s health condition and forced him to step down that September.

The Social Insurance Agency, blamed for sloppy management of massive amounts of pension data, was then reorganized into the Japan Pension Service to refresh its badly tainted image.

The government-linked JPS, which now has 12,000 workers, is a special organization affiliated with the Health, Labor and Welfare Ministry.

When asked if welfare minister Yasuhisa Shiozaki should be sacked to take responsibility for the incident, Suga said, “No, I don’t think so.”

“I’d like him to exert leadership” in carrying out an investigation and bolstering data security regarding the pension system, he added.

Meanwhile, the Democratic Party of Japan, the largest opposition force, said Tuesday it will not attend any Diet sessions to deliberate government-sponsored bills until the Abe administration releases the results in its investigations into the latest incident and demonstrates efforts to prevent a recurrence of the breach.

“We cannot continue ordinary deliberations of bills,” DPJ Diet affairs chief Yoshiaki Takagi told a news conference.

A DPJ boycott is likely to delay deliberations of some key government bills, including one to ease employment regulations on workers dispatched by temporary staff agencies.

The ruling bloc was just about to pass the controversial bill in the Lower House.

The bill would scrap the three-year limit on hiring temp workers to perform the same job as a full-time worker, thus enabling corporations to use temps for as long as they want instead of having to hire them as regular employees after a set period.

The DPJ and other opposition parties have opposed the bill.

The pension scandal could also affect another government-sponsored bill to create the My Number system, which involves allocating a 12-digit unified ID number to everyone covered by the public social security system.

Some critics have argued that the creation of the My Number system would hand the government too much power to monitor individuals and also increase the risks of leaks from and abuse of various data about individuals.