By Marc Jones

BERLIN (Reuters) - Germany's double Olympic champion Britta Steffen set a world record in the 100 metres freestyle on Thursday but predicted it would not last long and complained that futuristic swimsuits were damaging the sport.

Steffen, who won Olympic gold in the 50 and 100 metres freestyle in Beijing last year, won the preliminary heat of the German national championships in Berlin in 52.85 seconds, beating the mark of 52.88 set by Australia's Libby Trickett in March 2008.

"I feel really good, I'm in good shape and the new swimsuit gives me an extra boost," Steffen said.

Steffen said the record would last only until the world championships in Rome starting next month. She also lamented the impact high-tech swimsuits were having on swimming even though it benefited her on Thursday.

"This development is a shame for the sport -- where will it all stop?" Steffen said. "My new suit is like something from another planet, it's like a space suit."

The high-tech suits are controversial. As well as drawing the ire of swimming purists, some swimmers are now complaining the suits, rather than ability, are the key to winning.

Covered with fabics such as polyurethane to aid buoyancy, the body suits have helped set more than 100 world records in the past 18 months.

This week swimming's governing body, FINA, threw out Alain Bernard's 100 freestyle record set in April on the grounds he was wearing a swimsuit that had not been approved.

"It's like swimming on a mattress of air. In the suit I'm over a second quicker," said Steffen.

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