Team principal Christian Horner told reporters on Wednesday that suspicions were raised at the Circuit de Catalunya last weekend when Ferrari's Fernando Alonso [ Images ] pitted every time Red Bull called in Australian Mark Webber [ Images ].
"I don't know whether mechanics were putting their hands in their pockets at the wrong time or somebody was picking a tyre up," he said. "So we've just changed our procedure this weekend to be less transparent."
The team's suspicions were heightened when Red Bull pretended they were about to call in Webber, who was behind Alonso on the track, but did not do so while the Ferrari entered the pit lane.
Webber ultimately finished fourth, behind both McLarens and his team mate Sebastian Vettel [ Images ], while Spaniard Alonso ended up fifth and lapped.
"There were some comments (after Sunday's race) about Ferrari spying on us which I think have been misinterpreted," said Horner.
"I think Helmut (Marko, a close adviser to Red Bull's billionaire owner Dietrich Mateschitz) was convinced that they knew when we were pitting, which they did," he added.
Austrian Marko was quoted as saying after the Spanish Grand Prix that "we have noticed that Ferrari are doing some kind of espionage."
A Ferrari spokesman said they were just carrying out 'normal strategy', keeping a close watch on their rivals in the knowledge that Alonso had to pit on the same lap as Webber to stay ahead of him.
Horner did not suggest Ferrari were doing anything underhand but had seen "something that we were doing that was giving away when we were going to stop, and would call Fernando. It wasn't coincidence."
"Every time we called Mark in, Fernando would come down the pit lane," Horner said.
"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's got a Ferrari right ahead of him."
Horner added that the calls to Webber were made pretty late but Ferrari were still able to respond.
"In the end we made a dummy call (in Spain) and Fernando came in, Mark stayed out. But unfortunately by that time he had lost so much time to Jenson (Button) and Lewis (Hamilton) that a podium wasn't possible."
Horner said Red Bull, like all teams, listened in to the television broadcast feed for snippets of conversation from rivals.
The governing FIA and commercial rights holder Bernie Ecclestone's [ Images ] Formula One Management (FOM) receives encrypted radio traffic from all teams and occasionally makes some of it public during the race.
Teams cannot, however listen in to each others' communications.
"The radios tend to be encrypted, and digital radios these days, so... to hack a radio would be very difficult," said Horner. "So the teams are listening to the transmissions from FOM.
"Sometimes Fernando Alonso likes to talk in Italian.. All the teams are listening to the (FOM) transmissions... because obviously if there is something that can be gleaned from that then it's knowledge that's useful for strategic decisions."