Furor over a flawed labor ministry probe into the government-proposed discretionary labor system intensified Thursday after it was revealed that the survey contained at least 117 errors.

This latest development further erodes the credibility of data underpinning Prime Minister Shinzo Abe’s campaign to reform Japan’s work style.

Opposition lawmakers ratcheted up condemnation of the evolving data scandal, with Seiji Osaka of the Constitutional Democratic Party saying labor minister Katsunobu Kato should resign if any further shortcomings in the 2013 survey are discovered.

Scrutiny of the survey by Osaka and other opposition lawmakers found that it contained at least 117 errors that further cast doubt on its credibility, the lawmaker told the Lower House Budget Committee. Kato admitted those figures are in fact “impossible” during Wednesday’s Diet session.

“At the moment, we know there are at least 177 errors in the survey, but we don’t know how many more may turn up upon closer inspection. Any further revelation of shortcomings will call into question Minister Kato’s position,” Osaka said.

Abe rejected calls for Kato’s resignation, saying he expects the minister to announce the result of the ministry’s ongoing probe into the survey soon.

In one survey blunder, according to Kyodo News, an employee was described as having clocked 45 hours of overwork in a day, while the same individual’s monthly overtime was somehow reduced to 13 hours and 24 minutes — a discrepancy that points to human error and sloppy data processing.

Under the discretionary labor system, employees are paid according to a pre-determined number of hours instead of actual working hours. Abe’s government has argued it would give workers flexibility in deciding their actual working hours, but opposition parties have maintained it could lead to an increase in unpaid overtime and further the problem of karōshi (death from overwork).

The government has cited data from the survey in question over the past three years to emphasize the benefits of the discretionary labor system, which is a key proposal in Abe’s labor reform plans.

Citing the survey, Abe told the Diet in January that those who work under the system can work shorter hours than those who don’t. But he was forced to retract his comment last week as it emerged that the survey used two different methods to collect data, making it statistically unreliable.

On Wednesday, six opposition parties demanded the government not submit a labor reform bill as scheduled and instead conduct a thorough reworking of the 2013 survey, to ascertain how many hours were actually worked by those under the discretionary labor system.

In another revelation, while speaking to the Lower House committee on Thursday, Kato confirmed that original response papers used in the survey, which he previously claimed had been discarded, have been found in a basement room at the ministry.

Aside from seeking to expand the discretionary labor system, Abe’s work-style reform campaign aims to redress Japan’s culture of long working hours by placing an annual 720-hour cap on legally permissible overtime hours and introducing penalties for firms that don’t comply. It also wants to close income disparities between full-time and part-time workers under the mantra of “equal pay for equal work.”

“Our society can no loner remain one where people boast how many hours of overwork they did. It has to change fundamentally,” Abe said.