Just two meetings after he was docked the point she earned in the San Marino Grand Prix, Ralf Schumacher has found himself on the end of another penalty, this time for using the wrong tyres in Monaco free practice.

The German allegedly used a front tyre not officially allocated to his car and will have to add half a second on to his aggregate qualifying time. Tyre supplier Michelin has blamed human error for the mix-up, admitting that the tyres were incorrectly marked, resulting in Schumacher's car being fitted with one tyre not passed for his use at scrutineering.

The rogue tyre was identical to the one that should have been used, so no performance advantage was gained, but the F1 tyre rules are explicit and any breaches of Article 75d of the sporting regulations, which deals with tyre marking, are taken very seriously. Michelin later issued an apology to the team and 'in particular to Ralf Schumacher'.

Schumacher was ninth fastest in free practice on Thursday, quicker than both of his Toyota team-mates, Ricardo Zonta and defending Monaco champion Jarno Trulli..

"We had a pretty good day and completed a lot of laps, getting through all our work without any problems," the German reported before being summoned, along with Toyota personnel, to meet with the stewards, "We still obviously have work to do on set-up but that's always the case in Monaco.

"We'll also have to have a good look at the data to make our final tyre choice, but I'm still relatively optimistic for the rest of the weekend. We will be hoping for another strong points finish and doing everything to see if we can make the podium."