Nico Rosberg has added his voice to those of some of his fellow competitors in suggesting the advent of KERS (Kinetic Energy Recovery Systems) will penalise Formula 1's taller and heavier drivers in 2009.

The minimum weight for car and driver must be no less than 605kg, and the new energy-saving devices are set to weigh anywhere between 25kg and 40kg, meaning drivers now have even less scope to move ballast around the car to achieve an ideal weight distribution.

Alongside Rosberg - who measures 178cm tall and weighs 70kg - 2007 F1 World Champion Kimi Raikkonen, double title-winner Fernando Alonso, Honda refugee Rubens Barrichello and six-foot tall BMW-Sauber star Robert Kubica have all deliberately lost weight over the winter in preparation for the arrival of KERS.

The latter already lost several kilograms in the build-up to the 2008 campaign to weigh less than 70kg, and the Pole has insisted he cannot afford to lose any more should it lead to a consequent deterioration in his fitness or strength, according to Cologne-based newspaper Express.

Rosberg, whose opinion it is that a variable weight limit should be introduced - based upon the individual weight of each driver, so that none are unfairly disadvantaged - clearly agrees that the rule needs looking into.

"I have lost weight and even at Christmas was counting calories," the young Williams ace told German magazine Speedweek. "I think the weight rule is unfair because bigger drivers are disadvantaged even before they start [the season].

"I think it should be urgently talked about in the GPDA (Grand Prix Drivers' Association)."

Kubica's BMW team-mate Nick Heidfeld and Raikkonen's fellow Ferrari star Felipe Massa are both understood to weigh less than 60kg.