Hot on the heels of being told that he is not yet Britain's number one driver, Jenson Button has come under attack from his own team-mate.

Just days after David Coulthard tried to assert his status as the UK's top man in Formula One by telling the media that Button only beat him in San Marino courtesy of a superior car, Jarno Trulli has compared the youngster unfavourably against former team-mate Heinz-Harald Frentzen.

Trulli and Frentzen were team-mates at Jordan before the German was unceremoniously fired in the middle of 2001. Now with Arrows, while Trulli joined Button at Renault, the German is in no position to compete with his British counterpart - although Trulli reckons there is no comparison.

"Jenson's a good bloke and he's doing a great job [this season]," he told Italian magazine Autosprint, "but I've had stronger team-mates - like Frentzen."

Button currently has eight world championship points to Trulli's no score, and lies in fourth place behind Michael and Ralf Schumacher and his replacement at Williams, Juan Pablo Montoya. Trulli, true to his reputation, has been the better qualifier, however, winning 3-1 on current performance.

Trulli and Button have had their fair share of run-ins in the past - including celebrated collisions at Spa, Indianapolis and Monza - but insist that their partnership at Renault is a strong and harmonious one.