Image copyright AFP/Getty Images Image caption Suzuki confessed to slipping a prohibited substance into his teammate's water

Japan's anti-doping agency has banned a top kayaker for eight years after he admitted to drugging a rival.

Yasuhiro Suzuki, 32, admitted spiking Seiji Komatsu's drink with a banned drug before a domestic race to boost his own chances to qualify for the 2020 Olympics in Tokyo, the agency said.

Komatsu was disqualified after testing positive but the disqualification was later nullified.

Japan's Canoe Federation is considering expelling Suzuki permanently.

"Suzuki's conduct is totally contrary to the spirit of sporting fair play," it said in a statement.

Japanese sports officials said Suzuki had a history of sabotaging competitors, and had been known to steal their equipment.

According to the federation, Suzuki confessed to investigators that he had slipped a a prohibited muscle-building drug into the water of his faster teammate, 25, before the race in September.

"I was fretting," Suzuki was quoted as telling the federation. "I did it as I thought he would overwhelm me. I didn't expect he'd actually test positive," .

"It is extremely regrettable," Japan Sports Agency commissioner Daichi Suzuki was quoted as saying by Asahi Shimbun newspaper. "It is the kind of thing that has never been heard of in Japan's sporting history."