Grant Hackett obliterated the 1,500 metres world record as Australia deposed the United States as number one nation on the final day of the world swimming championships in Edmonton, Canada yesterday.

Defending champion Hackett demolished the world mark fellow Australian Kieren Perkins set nearly seven years ago, producing a swim of extraordinary pace to carve more than seven seconds from Perkins' time.

Hackett, who beat Perkins in Sydney last year to succeed him as Olympic champion, was inside world record pace all the way and powered home in 14 minutes 34.56 seconds to beat the 14:41.66 mark Perkins set at the Commonwealth Games in Victoria, Canada, in August 1994.

The final session ended appropriately with an Australian victory over the US in the women's 4x100 metres medley relay as Australia emerged top nation in the pool at the world championships for the first time, beating the Americans 13-9 in the title count.

Triple Olympic champion Inge de Bruijn sped to another golden treble, once again romping away from the opposition to add the 50 metres freestyle title to the 100 freestyle and 50 butterfly.

The 27-year-old Dutchwoman won the 50 freestyle in 24.47 from Sweden's Therese Alshammar, whom she beat twice at the Olympics and twice again in Fukuoka.

Ukraine pulled off an excellent double, with Oleg Lisogor outsprinting more fancied rivals to win the men's 50 metre breaststroke in 27.52 and Yana Klochkova scooping her second title of the meet in the women's 400 freestyle.

Klochkova, who had retained her 400 individual medley crown on the opening day, powered to victory in 4:07.30, nearly two seconds from Costa Rican Olympic bronze medallist Claudia Poll.

Alessio Boggiatto brought Italy their second individual medley gold of the championships, beating Americans Erik Vendt and Tom Wilkens to win the 400 individual medley by more than two seconds in 4:13.15.

Three days earlier, Italy's Olympic champion Massimiliano Rosolino had won the 200 event.

But it was Hackett who delivered the swim of the night and one for the memory after playing second fiddle to Ian Thorpe in the 400 and 800 freestyle events.

Hackett, who had joined forces with Thorpe in a world record breaking 4x200 freestyle relay on Friday, for once had the spotlight to himself.

He was inside world record pace all the way, slicing away at the Perkins time as he reeled off the 30 lengths in pool swimming's longest race, roared on by his team mates and the crowd at the Marine Messe indoor pool.

When Hackett hit the wall, only two other swimmers in the eight-man final finished on the same length, Britain's Graeme Smith in taking the silver in 14:58.94 and Russia's Alexei Filipets the bronze in 15:01.43.

Perkins, working as a television commentator, gave Hackett a "thumbs-up" acknowledgement after a stupendous swim.

"To take seven seconds off the record, I never expected that in a million years," Hackett said. "I thought only Ian Thorpe could do things like that.