Helmut Marko insists Mercedes' Pirelli tyre test was worth at least a second a lap

Red Bull advisor Helmut Marko has blasted Mercedes' tyre test in Spain, insisting the extra experience of the Pirelli compounds was easily worth a second per lap.

Christian Horner is one person looking for such clarification and the Red Bull Team Principal is upset at what he perceives to have been the "underhand" staging of the test. "What annoys me is that it was so underhand, and it makes a mockery of the rules," Horner told reporters. "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 not a transparent manner, 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. Irrelevant of what you call it, that's testing."