Red Bull launch protest

Red Bull has launched an official protest against Mercedes in the wake of their rivals conducting a secret tyre test with Pirelli.

The move comes ahead of the Monaco Grand Prix, with Red Bull team principal Christian Horner citing a lack of transparency.

"We feel it's not in line with the rules so that's why we've protested before the race. We just want clarity," said Horner.

Under the sporting regulations in-season testing is banned, however, it is understood in Pirelli's tyre-supply contract they are allowed private tests with individual teams should circumstances require.

With Pirelli due to slightly alter the structure of their rubber on safety grounds from next month's Canadian Grand Prix, and with tyres for 2014 due to change considerably given the new engine regulations, the Italian manufacturer felt it crucial the tyres were tested.

Despite that, it is the manner in which the test has taken place that angers Horner, who only discovered the situation on Saturday night.

He added: "There is confusion between what is contractually permissible and what a team is allowed to do in the sporting regs.

"It's a situation we need clarification on, and our position is we are going to request that clarification.

"I can understand Pirelli wanting to test the tyres, they've obviously got issues with the tyres.

"What's disappointing is it's been done in a manner that is not transparent, that a three-day test has taken place with a current car running on tyres that are going to be used at the next grand prix. Irrespective of what you call it, that's testing."