Formula One's ruling body has clarified the rules on dangerous racing moves by drivers defending a position in the heat of a race, giving the benefit of the doubt to the man who is leading.

The ruling comes after several controversial incidents this year in which drivers have vigorously defended their positions and, in some cases, forced challenging rivals off the circuit.

One of the most publicised came at the Bahrain Grand Prix when Nico Rosberg of Mercedes robustly defended his position from attempts to pass by Lewis Hamilton in a McLaren and then Fernando Alonso of Ferrari.

Both challenging drivers felt aggrieved at the way in which Rosberg moved his car to defend his position, forcing them to run wide and, in Hamilton's case, off the circuit completely.

The stewards investigated but took no action because they decided no "significant part" of either Hamilton or Alonso's cars was alongside Rosberg at the time.

The incidents created uproar, however, and many drivers called for a clearer explanation of what might be considered to be a "significant part" of a car.

Charlie Whiting, the race director of the ruling body the International Motoring Federation (FIA), has now made clear that "any driver defending his position on a straight, and before any braking area, may use the full width of the track during his first move provided no significant portion of the car attempting to pass is alongside his.

"Whilst defending in this way, the driver may not leave the track without justifiable reason."

To clarify the ruling, he added: "For the avoidance of doubt, if any part of the front wing of the car attempting to pass is alongside the rear wheel of the car in front this will be deemed to be a 'significant portion'."

This, in effect, means that an attacking car has to find a way to move the front wing of his car alongside the rear wheels of the defending car to be able to claim that he is in a position to overtake -- and that the defending driver cannot move around to defend that position.

Rosberg can rest easy because in both cases in Bahrain he defended his position without breaking the rules.