The Japanese government is considering postponing by one year the implementation of parts of a labor reform bill after acknowledging fundamental flaws in its work hours survey, sources close to the matter said Wednesday.

Opposition parties have accused the government of deliberately designing the survey to make it look like expanding the “discretionary labor” system would help lessen Japan’s chronic overwork problem. They argue it could have the opposite effect.

Prime Minister Shinzo Abe has apologized for citing the erroneous survey in Diet debate.

Under the discretionary labor system, employees are given a fixed number of overtime hours and are paid on the assumption they worked those hours, meaning any further overtime goes unpaid.

The government says it would lead to a more flexible working environment, and business lobbies support the move. But labor unions say it could worsen a culture of overwork that has led to suicides and other deaths.

According to the sources, the year-long delay would apply to the expansion of that system and the start of a separate system allowing certain high-paid professionals to be exempted from a legal overtime cap. Both would come into effect in April 2020 instead of April next year.

The government has decided it needs more time to properly prepare for the changes, including by making sure employers are fully informed, the sources said.

But opposition parties are trying to seize on the delay to support their argument that the contentious provisions should be removed from the working practices reform bill altogether.

The bill has yet to be formally introduced to the Diet, and debate on labor reform by the House of Representatives Budget Committee has so far been dominated by the survey.

The survey on working hours conducted by the labor ministry in 2013 concluded that the average worker on a discretionary labor contract generally works shorter hours than one on a conventional contract.

But the ministry said this week it used two different methods to collect the respective data, making the survey statistically unsound.

A further 117 data errors have been found in the survey, ministry officials said at a meeting held by six opposition parties to discuss the matter.

The officials also revealed that the original response papers used in the survey have been found in a basement room at the ministry.

Asked about the response papers’ whereabouts on Wednesday last week — the same day Abe retracted his remark citing the survey — Kato said the materials were “gone.”

The ruling and opposition parties agreed Wednesday to hold an intensive committee session on labor reform Thursday afternoon, which will include Abe among the participants.

Separately, Abe told Kato to be sure to work closely with the rest of the Liberal Democratic Party on the bill from now on.

The secretaries general of Abe’s LDP and the smaller Komeito party, which make up the ruling coalition, agreed to thoroughly pick over the contents of the bill before putting it up for Cabinet approval, after which it can be formally debated in the Diet.

The Ministry of Health, Labor and Welfare is aiming to get the bill approved by the coalition next week so it can be submitted to the Diet early next month.

Fired up by the survey issue, opposition lawmakers are likely to fight the bill at every turn, meaning its passage could be delayed until June at the earliest. The current Diet session is set to end in late June.

At their meeting on Wednesday, the six opposition parties agreed to demand that the government not submit the bill in its present form during the current session.

They also agreed that a new survey should be carried out to determine how many hours those in the discretionary labor system really work.