TOKYO (Kyodo) -- Japanese Prime Minister Shigeru Ishiba on Friday came under fire for his distribution of gift vouchers worth 100,000 yen ($676) each to rookie lower house members of his scandal-mired ruling Liberal Democratic party.

Opposition party leaders questioned the legality of Ishiba's handing out the vouchers ahead of a March 3 dinner meeting at his official residence, ramping up pressure on the premier to fully explain himself. Some opposition members demanded he step down.

Ishiba acknowledged being out of touch with public sentiment and apologized for causing trouble. But he said the vouchers he paid for were intended as tokens of appreciation, not donations, for the families of the lawmakers who were elected for the first time in a general election last year.

The revelation deals a blow to Ishiba, who became LDP chief and therefore prime minister about five months ago with a pledge to restore public confidence in politics damaged by a series of money scandals affecting his party.

It also came at a crucial time for the minority government, as parliamentary deliberations continue on a draft budget plan for the new fiscal year starting April 1. Under grilling by opposition lawmakers in parliament, he said he had distributed vouchers around 10 times before.

"If he cannot dispel suspicions, he cannot stay on as prime minister," said Yuichiro Tamaki, head of the Democratic Party for the People, a small opposition party that has been taking an increasingly cooperative stance toward the ruling coalition of the LDP and the Komeito party.

Criticism also came from another opposition party whose support in parliament paved the way for the fiscal 2025 draft budget to clear the House of Representatives last week.

"It is a bribe of some sort. It's totally inappropriate, and he should seriously reflect on his behavior," Seiji Maehara, the co-head of the Japan Innovation Party, told reporters.

All 15 lower house members who attended the meeting with Ishiba were elected in the Oct. 27 election that stripped the ruling coalition of their majority control of the powerful chamber. Another national election, for the upper house, or the House of Councillors, is slated for this summer.

Ishiba's staff delivered vouchers to the offices of the first-term members on March 3, hours before they met over dinner at the prime minister's official residence, according to participants.

All of them later returned the vouchers, according to sources with knowledge of the situation.

"I paid for the vouchers myself, which were meant to express my appreciation," Ishiba told reporters on Friday.

"There are no legal problems concerning this," he said, insisting that they were not political donations prohibited by the law.

The political funds control law bans donations by individuals to politicians to support their political activities.

Ishiba also said he did not violate the Public Offices Election Act, which prohibits politicians from giving donations, both money and goods, to people in their constituency.

But Komeito chief Tetsuo Saito suggested the move was inadvisable. "We should refrain from doing something that cannot be understood by ordinary people," he said.

Earlier this week, Shoji Nishida, an upper house member of the LDP, called for Ishiba to be replaced, fearing that the LDP will not be able to fight the forthcoming election under the current party chief.