Feb. 17 (Bloomberg) -- Japanese Finance Minister Shoichi Nakagawa said he will submit a certificate to parliament in an effort to explain how medications he took caused his slurred speech and drowsiness at a press conference in Rome last week.

“I was in really bad condition and I deeply apologize for causing trouble,” Nakagawa said in Tokyo today. “I would like to keep doing my assigned job.” He said he planned to hand the document to the Diet later today.

The opposition Democratic Party of Japan plans to submit a censure motion against Nakagawa, after television footage showed him slurring his speech and nodding off at the briefing that followed a Group of Seven meeting on Feb. 14. Nakagawa yesterday denied he was drunk and said he has no plans to resign.

Prime Minister Taro Aso met with Nakagawa last night and later told reporters the finance minister has been doing “an incredibly good job” and should “take good care of himself.” The incident is the latest blow to Aso, whose popularity slid to 9.7 percent in a Nippon Television news survey, the second worst on record for a Japanese leader.

Nakagawa yesterday attributed his behavior to taking more medication than prescribed after drinking “a sip” of wine at lunch. Today, he said the medicine probably included antibiotics and a stomach drug. He said he also took an antihistamine and a back pain reliever and a doctor last night told him the two drugs, combined with jet lag, may have affected his health.

He said he would take the medication to a doctor today to obtain the diagnosis. He couldn’t recall the names of the drugs.

The morning session of the lower house budget committee was canceled due to Nakagawa’s medical appointment, the Diet secretariat said.

To contact the reporter on this story: Keiko Ujikane in Tokyo at kujikane@bloomberg.net

Last Updated: February 16, 2009 21:21 EST