Red Bull has changed its pit stop procedure ahead of this weekend's Monaco GP in the belief that Ferrari is copying its strategy.

Speaking in Monaco, team boss Christian Horner said that suspicions were raised last weekend in Spain when the Italian team appeared to mirror the Austrian outfit's strategy, Fernando Alonso stopping every time Mark Webber was called in.

"I don't know whether mechanics were putting their hands in their pockets at the wrong time or somebody was picking a tyre up," said the Englishman. "So we've just changed our procedure this weekend to be less transparent.

"Every time we called Mark in, Fernando would come down the pit lane," Horner continued. "I think that is probably more likely to do with one of our procedures or movement in the garage, which is absolutely allowed. It was obviously quite frustrating for Mark that every time he came into the box, he'd got a Ferrari right ahead of him."

At one stage, fearing that its Italian rival was copying its strategy, the Milton Keynes outfit made out as if to call in Webber - who was running behind Alonso - while the Spaniard dived into the pitlane the Australian driver remained on track.

"We made a dummy call and Fernando came in, and Mark stayed out. But unfortunately by that time he had lost so much time to Jenson and Lewis that a podium wasn't possible.

"There were some comments about Ferrari spying on us which I think have been misinterpreted," said Horner. "I think Helmut (Marko) was convinced that they knew when we were pitting, which they did."

Ferrari has dismissed the claim, saying that while it does pay close attention to its rivals it was simply carrying out its normal strategy in Spain. At last year's Abu Dhabi Grand Prix, the Italian team virtually lost the championship for Alonso when it shadowed Red Bull's strategy.