Australia’s Emma McKeon has set a new national record to claim 100m butterfly silver at the world swimming championships in Budapest.

McKeon – Australia’s most decorated Rio swimmer with four medals – clocked 56.18 seconds but could not reel in Sweden’s Olympic champion and world record holder Sarah Sjostrom (55.53).

On the second night of the eight-day titles at Duna Arena, McKeon eclipsed the national mark she shared with Jessicah Schipper’s 2009 supersuit time (56.23) in the 100m butterfly final.

However, Sjostrom – still buzzing from shattering Australian Cate Campbell’s world 100m freestyle world record on Sunday night – would not be denied.

Sjostrom claimed her fourth 100m butterfly world crown.

“This is the least nervous I have been at a meet – I think it mostly comes down to being happy and enjoying what I am doing,” McKeon said.

It was the third straight race at Budapest that McKeon had lowered her 100m butterfly personal best time.

McKeon also collected her second medal of the meet to date.

She was a member of Australia’s 4x100m freestyle relay team that claimed silver on Sunday night.

After two days, Australia have a total of three silver to be fifth on the swimming medal tally behind leaders the United States (three gold, two silver, one bronze).

In a demanding world titles schedule, McKeon will also contest the blue riband 100m and 200m freestyle events in Hungary plus another two relay events.

Sweden’s Sarah Sjostrom (top) beats Australia’s Emma McKeon to 100m butterfly gold. Photo: AAP

Meanwhile, dual defending world champion Emily Seebohm qualified second fastest for Tuesday night’s 100m backstroke final.

Seebohm — who is also the 200m backstroke defending champion in Hungary — clocked 58.85 seconds in the semi-finals to trail world number one Kylie Masse of Canada (58.18) ahead of the medal race.

Seebohm’s 100m backstroke world title defence has been boosted after Olympic champion Katinka Hosszu of Hungary withdrew from the event to concentrate on Monday night’s 200m individual medley final.

Three-time Olympic gold medallist Hosszu fell short of her world record but still cruised to her third straight world 200m IM crown in front of her adoring public.

Seebohm’s partner and fellow dual world defending champion Mitch Larkin (53.19) qualified sixth fastest for Tuesday night’s 100m backstroke final behind pace setter Xu Jiayu of China (52.44).

And Mack Horton notched a personal best in the 200m freestyle of one minute and 46.81 seconds but failed to make Tuesday night’s final.

Olympic 400m freestyle champion Horton was 11th fastest after the 200m semis, with Briton Duncan Scott (1:45.16) topping the timesheets.

Horton — who claimed 400m silver on Sunday night – was a surprise 200m competitor at Hungary after upsetting Cameron McEvoy and Kyle Chalmers at April’s selection trials.

“I think it came down to inexperience in 200m racing,” Horton said of his semi-final finish.