he move by the Japan Restoration Party threatens to complicate efforts by the cross-party lobby, which had set its timetable in part to avoid making the controversial issue of casinos a focal point ahead of upper house elections in July.
The JRP, which has 16 lawmakers in the 140-member lobby, is keen to take the initiative on the issue in the run-up to the election, according to one of the sources, who spoke on condition of anonymity ahead of the bill's submission.
No one at JRP's offices could be reached for comment.
Hopes were lifted by the return to power in December of the business-friendly Liberal Democratic Party under Prime Minister Shinzo Abe, who has indicated he is open to the idea of casino resorts as part of his strategy for driving economic growth.
Broker CLSA estimates Japan's gaming market could be worth us$ 10 billion if two large integrated resorts were developed - bigger than gambling revenues in Singapore and Las Vegas.
Outspoken Osaka Mayor Toru Hashimoto, co-leader of the JRP, has been vocal about wanting to develop casino resorts to help boost the economy of western Japan, and had in the past held out the option of the JRP submitting a bill on its own.
But the JRP participated in an April re-launching of the cross-party lobby, leading many to believe it would act in unison with the group.