SYDNEY (AFP) - World 100m freestyle champion James Magnussen - who led the much-vaunted 4x100m Australian relay team which bombed spectacularly at the 2012 Olympics - has claimed taking sleeping tablets was "a tradition".

The team last week admitted taking the prescription drug Stilnox, banned by the Australian Olympic Committee (AOC), as part of a "bonding exercise" ahead of the Games in London, where they failed even to reach the podium.

In an interview with Channel Seven aired late Sunday, Magnussen said during dinner that the discussion had turned to what previous relay teams had done to bond and the group had collectively decided to take the drug.

"The tradition had been, and what we did, was take Stilnox on its own with water," he said.

Use of the drug had been discouraged as far back as 2005, according to The Australian newspaper, which said former relay swimmers Michael Klim, Ashley Callus and Andrew Lauterstein had all denied taking it as a bonding tradition.