Burnett was seventh in the 200m freestyle at the 2004 Olympics

Commonwealth 100m freestyle champion Simon Burnett failed in his final attempt to qualify for an individual event in Beijing at the Olympic trials.

Burnett had already missed out in the 50m and 200m freestyle and he tired to finish third in his 100m heat.

Swimmers have to achieve the Olympic qualifying time during the heats and having failed to do so the best Burnett can hope for is a place in the relay.

Only Ross Davenport managed to reach the qualifying time.

In addition to achieving the qualifying time in their heats, swimmers then need to finish in the top two in the final to gain selection.

Burnett finished sixth fastest to qualify for the final on Saturday morning - and so could qualify for the 4x100m relay.

It is a big disappointment for the 24-year-old, who finished seventh in the 200m freestyle at the Olympics four years ago.

"The past two years have been very difficult. It has been a downward spiral," said Burnett.

"There have been glimmers of hope, and then huge lows.

"I find one thing, change it and go to the next meet, and then it is worse than the previous meet.

"The most frustrating thing is not being able to figure it out.

"It's like waking up in the morning and you find you don't know how to walk and then you wake up the next day and it's worse.

"You don't know what changed."

Lizzie Simmonds just failed to claim the British record in the heats of the 100m backstroke.

The five-time European junior champion was two seconds inside Katy Sexton's mark at the final turn but could not maintain it and touched in two minutes 08.79 seconds.

It was just 0.05secs outside the record and a personal best for the 17-year-old who has already qualified for the 100m version.

Gemma Spofforth, Stephanie Proud and Georgia Davies also gained the qualification time.

Kerry Buchan was fastest in the 200m breaststroke heats but failed to gain the qualification time.

World silver medallist Kirsty Balfour had been pre-selected.

Olympic and world bronze medallist David Davies was also pre-selected in the 1,500m freestyle.

In his absence, Richard Charlesworth of Hatfield and Loughborough's Daniel Fogg claimed the qualification time.