The advertising watchdog has rapped Citroen UK over the knuckles because some cyclists featured in a TV ad for its C4 car weren't wearing cycle helmets.

Citroen said ithad featured cyclists in the ad to demonstrate the low CO2 emissions and 'stop-start technology' on the new C4, rather than focusing on cycling.

The message was that the C4's engine stopped when the vehicle came to a halt at traffic lights, which was less polluting and more comfortable for cyclists.

But the Advertising Standards Authority has ruled that because the cyclists in the ad weren't wearing cycle helmets, the ad "might encourage younger children to emulate a behaviour prejudicial to their health and safety" and ruled it should not be broadcast at times when younger children were likely to be watching.