Michael Phelps has shattered his own 400m individual medley world record at the world swimming championships in Melbourne.

Phelps slashed over two seconds off the mark he set at the 2004 Athens Olympics when he swum four minutes 6.22 seconds to claim his seventh gold of the meet.

It is Phelps' fourth individual and fifth world record of the meet.

He had earlier broken down the barriers in the 200m freestyle, 200m butterfly, 200m individual medley and 4x200m freestyle relay.

The American superstar was under world record pace in the opening butterfly leg but then dropped over one second behind his benchmark as teammate Ryan Lochte claimed the lead in the backstroke.

But Phelps asserted his dominance in his improving breaststroke leg to turn at the 300m mark with over a second advantage on his previous best time.

"I saw at the 150 I was a tenth (of a second) under (world record time) and I wanted to have a strong breaststroke leg," Phelps said after the race.

"I think that's probably my most improved stroke over the last six months to a year.

"It was my last race and I wanted to finish strong."

He powered home in the freestyle to take 2.04 seconds off the record, his dominance illustrated by the digital world record line on television monitors being well behind his feet as was the case in the 200m butterfly earlier this meet.

Lochte (4:09.74) settled for the silver medal with Italian Luca Marin (4:09.88) taking bronze.

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