Just what Prime Minister Taro Aso didn't need was another problem, but a new one landed on his plate Thursday when allegations emerged in a weekly magazine that Deputy Chief Cabinet Secretary Yoshitada Konoike has been having an affair.

According to Shukan Shincho, which went on sale Thursday, Konoike allegedly let a married woman stay at his Upper House dormitory in Chiyoda Ward.

The magazine claims the woman entered the dorm separately after Konoike with a key, and that Konoike's wife didn't stay in the unit that evening. The woman was seen leaving the next day, the story said.

Later in the day, Konoike denied having an affair with the woman.

"I can swear that there is no man-woman relationship with her," Konoike told reporters, adding the woman was a "family friend" whose husband he knows as well.

The deputy chief Cabinet secretary explained that on the evening of Jan. 6, he had been planning on meeting several people but the others ended up canceling and it became just him and the woman.

Konoike, however, admitted she has been in and out of his dorm and he gave her his key for a day or two before.

But she did not spend the night, he claimed.

Yukio Hatoyama, secretary general of the Democratic Party of Japan, urged Konoike to resign. But on Thursday morning, Kawamura said he didn't think resignation was necessary at the moment.

Konoike said he has no plan resign.

The allegations could heighten public criticism of Aso, since Konoike is a close ally and his job as deputy chief Cabinet secretary is to support the prime minister.