Between 260,000 and 340,000 foreign workers are estimated to flow into Japan in the five years from next April through an envisioned immigration control law revision aimed at dealing with the country's serious labor crunch, government sources said Tuesday.

The estimate was unofficially made available as opposition parties are criticizing the government for hastily moving ahead to pass the bill to revise the law without disclosing details, such as how many workers would be accepted and in which sectors.

Deliberations on the bill started at the House of Representatives the same day, with Prime Minister Shinzo Abe saying that the government will announce the official estimate "sometime soon."

According to the sources, the government is expecting a labor shortage of around 1.30 million to 1.35 million workers in the five-year period. For the fiscal year from April 2019 alone, it expects to accept about 33,000 to 47,000 foreign workers for an estimated shortage of more than 600,000 laborers.

The government is expected to release the figures on Wednesday.

Abe said at the lower house plenary session that the exact figures are "being examined now" but the estimate will serve as a ceiling for the number of foreign workers to be accepted under the new system unless there is a major change in the economic situation.

The government aims to pass the bill during the ongoing parliamentary session through Dec. 10, with an eye to introducing the new program from April next year.

The bill would create a new visa status for foreign workers in various sectors deemed seriously short of labor, possibly ranging from construction and farming to nursing care.

The system, under certain conditions, could pave the way for foreign workers to live permanently in Japan. It has stirred controversy as being a major policy shift for Japan, which has largely restricted imported labor.