Child sex abuse: Is there a right age of consent?

Is there a right age of consent? A bill introduced in the French parliament would set the minimum age at 15 for consensual sex with an adult. The law here bans sex with a minor, but that carries a much lighter sentence than in Anglo-Saxon countries where it's automatically considered statutory rape. Why not here? Child sex abuse is an abuse of power, mighty adults imposing their will on minors. The issue's been brought to a head in France by some recent high-profile cases.