Australia's five-time Olympic swimming champion Ian Thorpe is back in the pool and has not ruled out a return to competitive action in time for next year's London Games.

Thorpe, 28, who retired in 2006 citing waning motivation, has been training to recuperate from a shoulder injury suffered in a car accident in China more than two years ago.

Thorpe's manager, David Flaskas, has confirmed Thorpe has been training, but he also made it clear that if he were to return to competitive swimming, it would not happen overnight, newspapers reported.

Flaskas said they had not spoken specifically about the 2012 London Olympics.

He said for Thorpe to return to competitive swimming he would have to be reinstated on the international drug-testing register at least nine months before competing.

"He's loving swimming all over again, but he's not asked me to apply to Australian swimming to get into the drug-testing regime," Flaskas said.

"I still think he's got competitive juices but he also understands what it takes to compete at the level he competes at.

"There's a lot of water to pass under the bridge but the one thing he is doing is enjoying it and, as he has said before, you never say never."

Flaskas said Thorpe was injured in a car crash during the Beijing Olympics