Five-time Olympic gold medallist Ian Thorpe said Saturday Australia's poor showing at the London Games had not dampened his comeback hopes and he expected his homeland to quickly return to form.

Thorpe, 29, failed to qualify for London at March's Olympic trials, little more than a year after announcing ambitious plans to come out of retirement, and has been commentating on the Olympic swimming for the BBC.

He vowed to continue swimming despite the London setback and told Australia's ABC Television his compatriots' lacklustre Olympic campaign in the face of deep and fierce competition had not dimmed his enthusiasm for the pool.

"I'm still keen. This competition has changed swimming, and this has been coming for quite some time," Thorpe said.

"I'm more enthusiastic about it now because of watching those results, I love that the medals are going out (widely), that there's been a renaissance of performance in Europe as well.

"At the same time China's emerging as a swimming nation and they're being consistent with performances."

Thorpe admitted that he had been surprised at Australia's performance -- the first time it has failed to win an individual gold in the pool since 1976 -- with many swimmers failing to replicate their trial times.

Former head coach of Australia's swimming squad Don Talbot has warned it will take the side four to eight years to rebound from its "mediocre" performance, but Thorpe said he believed the golden days would soon return.

"I think Australia can take a position back close to where we were before, at some of the dizzying heights of success that we've had, but I think people's expectations have to be a little more realistic as well," said Thorpe.

"I think we've been too successful for too long and people have under-appreciated how much it actually takes to win a gold medal."

Known as the "Thorpedo", the Olympic great retired in 2006 after a glittering career in which he ruled the pool from 1998 to 2004, taking nine Olympic medals and 11 world titles and setting 13 long course world records.

He returned to racing last November in Singapore but had a string of disappointing results leading up to his ultimately unsuccessful London Olympic bid in March.

Thorpe is yet to decide where he will next compete, saying only that it will be "sometime this year". He has not ruled out aiming for the Rio Games in 2016.