TOKYO (Kyodo) -- The office of former Prime Minister Fumio Kishida distributed gift vouchers worth 100,000 yen ($670) each to parliamentary vice ministers during a 2022 meal gathering with the then-premier, ruling party sources said Wednesday, fueling speculation that gift-giving is a common practice among lawmakers in power.

The revelation comes as Kishida's successor, incumbent Prime Minister Shigeru Ishiba, faces scrutiny over his own distribution of vouchers worth 100,000 yen each as tokens of "appreciation" to new lower house members of the Liberal Democratic Party, which has been reeling from a political fundraising scandal.

According to the sources, Kishida's staff delivered vouchers to LDP lawmakers who, at the time, served as parliamentary vice ministers ahead of a meeting at the prime minister's official residence on Dec. 20, 2022.

Kishida's office told Kyodo News, "We always followed the law," without providing further details. He served as prime minister for three years from October 2021 before being replaced by Ishiba.

Japan's political funds control law bans donations by individuals to politicians for the purpose of political activities, and Ishiba has categorically denied that the vouchers his office distributed ahead of a March 3 dinner meeting at the prime minister's official residence were donations.

During Kishida's tenure, it emerged that some LDP heavyweights had underreported portions of their income from fundraising events.

The scandal eroded public trust in politics, becoming one of the critical factors that caused the ruling coalition to lose majority control of the powerful House of Representatives in an election last October, making Ishiba head of a minority government.

Opposition party lawmakers are turning up the heat on Ishiba and the LDP, with one lawmaker from the Constitutional Democratic Party of Japan demanding Kishida answer questions in parliament.

Asked whether he was aware of voucher-giving by past prime ministers, Ishiba told a parliamentary session on Wednesday that he does not have knowledge of it "at all." He also said, "I'm not in a position to give an answer, either."

Multiple LDP lawmakers and other sources said they also received vouchers worth 50,000 or 100,000 yen at meal gatherings during former Prime Minister Shinzo Abe's tenure. Abe served as premier from 2012 to 2020, following a brief term from 2005 to 2006.

As former prime ministers come under increased scrutiny over whether they distributed vouchers or other items during their tenure, the office of Yoshihide Suga, Abe's immediate successor, said that "souvenirs" were distributed, but no laws were broken.

The office of Taro Aso, who was prime minister between 2008 and 2009, declined to give a clear answer when asked by Kyodo News whether gift vouchers were distributed while he was in office.

"We handled it appropriately, taking into consideration the nature of meetings with parliamentarians," the office said.

The revelations have cast a shadow over parliamentary deliberations on the draft state budget for the next fiscal year starting in April and sparked public backlash over politicians' spending habits, which are seen as sharply contrasting with those of ordinary households struggling with inflation.

They also come ahead of an election this summer for the House of Councillors, the upper chamber currently controlled by the ruling coalition.

Yoshihiko Noda, who served as premier between 2011 and 2012 and now serves as CDPJ leader, told reporters he had "never" given out vouchers.

"This looks to be an issue with the LDP's political culture. It is shaping up to be a deep-rooted structural one," Noda said.

Ishiba has struggled to shore up waning public support for his Cabinet since becoming LDP chief and prime minister five months ago, vowing to restore trust in politics.

On Wednesday, a senior member of the LDP's junior coalition partner, the Komeito party, urged the ruling party to get things right. "If (voucher-giving) was habitual, then it is inappropriate," Komeito policy chief Mitsunari Okamoto said at a press conference.

An upper house member of the LDP said Sunday it was a "standard practice" followed by past prime ministers to distribute gift vouchers. But he later retracted the comment, saying it was not based on fact.