Graeme Smith believes Paul Biedermann has usurped Michael Phelps to become the greatest 200m freestyle swimmer in history.

The German produced a stunning swim last night at the World Championships in Rome when he beat the 14-time Olympic champion by a body length to inflict the first defeat on the American over four lengths in serious international competition since the Athens Olympics.

It followed up his equally astonishing effort on Sunday, when he clawed back a deficit of more than 1.2seconds on the final length to consign Ian Thorpe's 400m free record to history.

Both records had previously been considered untouchable alongside the 1500m freestyle mark set by Grant Hackett in 2001, which is also under threat at the Foro Italico.

Biedermann has acknowledged the role his Arena X-Glide suit has had to play in his performances but he was pulling away from the Speedo-clad Phelps at the end of the race, leaving the American in the unaccustomed position of having to attempt to be gracious in defeat.

Double Olympic medallist David Davies has called for swimmers to be given more credit, despite the performance-enhancing nature of the suits, something Smith echoes.

Smith, who was behind both Thorpe and Hackett in their record-breaking swims, told Press Association Sport: "I think Thorpe is still the best 400 freestyler of all time but possibly he (Biedermann) is the best 200 (freestyler) in history."

"This season he has had some great swims. I think some people are surprised he has broken the records but I'm not.

"Obviously when you are talking about Thorpe's and Phelps' records being broken you are a little bit surprised but if I had had to pick anyone in the field to do it, he would have been the first."

The Briton competed at three Olympics and four World Championships, where he won a bronze and silver, and, having raced Thorpe on a number of occasions, is well placed to comment.

He added: "I think probably Thorpe's time would still have stood if it was the old suits.

"I think in the 200 he (Biedermann) could have broken the record in any suit.

"His last 50 in the 400 was phenomenal.

"I've never seen anything as impressive as that.

"The suit probably does help a little bit but I think he is the best 200 and 400 swimmer at the moment - whether he is the best of all time is a debate which will rage on for many years."