A troupe of models streamed on to the court of the Madrid Masters tennis tournament on Monday -- and into the centre of a controversy about whether they were trivialising the competition.

The 19 to 28-year-olds were drafted in as ball-girls to replace the young fans who usually run around picking up stray balls and handing towels to players and will work in most of the televised matches at the tournament.

But despite winning applause from spectators, they had a mixed reception off-court.

Left-wing Madrid politician Ines Sabanes said employing the women, who wear skirts and tight tops emblazoned with the name of a sponsor, was sexist and frivolous.

Parents of the teenagers they ousted felt it was a heartless move. "This kills the children's dreams of sharing a court with their idols," said a 50-year-old mother.

Some fans fretted about the models' lack of experience -- most knew little about tennis before signing up for the job although they went through two weeks of theory and practical lessons to prepare for the high profile matches.

"I started from zero, apart from a bit of messing around on the beach," said Mercedes Munoz, 26, at a pre-game makeup session on Monday.

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The ball-girls they replaced, dressed in less glamorous black shorts and shirts, were unconvinced despite the training.

"We think its very, very bad, because in a game of tennis the centre of attention should be the player. It's sport, not a catwalk," said one 14-year-old who did not want to be named.

Only the players, more focused on winning than on ball-girls' looks, seem to have shrugged off the controversy.

"When you're on the court, you only look at the ball and your coach -- as long as its the same ball it doesn't matter (who throws it)," said Spain's Alex Corretja.