Japan's swimmers could face lifetime bans if they dye their hair, wear an earring or have brightly decorated fingernails.

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Japanese officials have launched a strict policy to prevent athletes turning up for competitions looking more like rock stars than swimmers.

Male and female swimmers caught sneaking into each others rooms at Japanese training camp, where the sexes have separate sleeping quarters, will also find themselves in hot water.

"The United States and Australia are also setting these criteria," said Japan Swimming Federation executive director Masafumi Izumi.

"We have had many recent controversies (in Japan) with marijuana in sport and at universities, and this is about swimming taking a stand on its own initiative."

The JSF's stringent new plan has been written into its charter following an executive board meeting on Tuesday and swimmers will have to sign a letter of oath.

Rule-breakers face being booted out of the team and sent home in disgrace, a suspension of up to five years or even a lifetime ban.

"It is more an enhancement of the rules," the JSF said. "It's a policy top swimming countries like Australia and the Americans follow."