Suspicions are growing that past prime ministers of the ruling Liberal Democratic Party (LDP) handed out money and gifts to party lawmakers in an opaque fashion.

It has emerged that former Prime Minister Fumio Kishida distributed gift vouchers worth 100,000 yen (approx. $668) each at a gathering with parliamentary vice-ministers at the prime minister's official residence while he was in office. The situation resembles Prime Minister Shigeru Ishiba's gift voucher scandal, in which his office gave out gift vouchers to 15 rookie LDP lawmakers who attended a dinner meeting at the PM's official residence.

There has been a spate of testimonials that gift vouchers were similarly distributed under the second administration of the late former Prime Minister Shinzo Abe. One LDP legislator who was first elected to the House of Representatives in 2012 has admitted to receiving cash vouchers in around 2013 during Abe's reign.

While Kishida and his predecessor Yoshihide Suga have stopped short of providing detailed explanations, the series of revelations have raised suspicions that such practices had become quite common within the LDP.

If that's the case, it means activities that may have violated the Political Funds Control Act continued for years. The possibility that donations in the name of "souvenirs" has been rampant, exploiting legal loopholes, cannot be ruled out.

Such lavish gift-giving is out of touch with public sentiment just when people are struggling with soaring prices. Opposition parties are grilling the administration over whether the Cabinet Secretariat's secret funds, which are sourced by taxpayers' money, were used to purchase those gift vouchers.

Although Ishiba has offered his "deepest apology" over the scandal, he has merely reiterated that he is not in a position to answer questions about how the past LDP administrations have handled the matter.

The prime minister would not be able to win understanding if he were to get away with the issue, treating it as if it were someone else's problem. He should instruct an investigation into those "customary practices" to get to the bottom of the allegations.

The LDP, to begin with, has notably been reluctant to carry out political funding reforms. The epitome of this is the party's attempts to retain political donations by companies and other organizations.

The LDP's faction slush funds scandal has brought into sharp relief how party lawmakers have racked their brains to raise murky funds to expand their influence.

Up until now, even the practice of handing out gift vouchers to party legislators had not been called into question within the LDP. One LDP lawmaker revealed that they had considered the vouchers as a "prize for their effort" in winning an election. There has been growing skepticism that the financial sense of the LDP as a whole has been paralyzed.

Ishiba has justified money-spending politics as "the cost of democracy." His explanation is unconvincing now that these money and gift transactions have come to the surface.

The LDP should be aware of the growing public distrust in its money-oriented party culture. Unless the LDP drastically revamps its attitude, it will in no way be able to restore public confidence.