The Red Bull and Ferrari teams on Sunday lodged protests against rivals Mercedes for taking part in a secret tyre test following the Spanish Grand Prix two weeks ago.

Red Bull chief Christian Horner confirmed his team had taken formal action just hours before the start of the Monaco Grand Prix where the Mercedes drivers, German Nico Rosberg and Briton Lewis Hamilton, started from first and second places.

Horner said he had only learnt about the test on Saturday night.

“I can understand Pirelli wanting to test the tyres,” he said. “They’ve obviously got issues with the tyres. What’s disappointing is it’s been done in not a transparent manner. A three-day test has taken place with a current car running on tyres that are going to be used in the next Grand Prix – and irrelevant of what you call it, that’s testing.”

Red Bull’s protest is under article 22.4 of the sporting regulations, which dictates that no on-track testing may take place during a season, other than a designated three-day ‘young driver test’ or straight-line aerodynamic testing.

In addition, according to Autosport, Ferrari have written to the sport’s ruling body, the International Motoring Federation (FIA), seeking clarification about the testing restrictions.

It was reported that Mercedes conducted 1000km of running during three days at Pirelli’s request.