The agency will create a campaign highlighting the scooters' exemption from the congestion charging, breaking early next year to capitalise on the inevitable media storm inspired by February's introduction of the charge.
However, it is understood that early negotiations with London Transport media owner Adshel have run into difficulties over Piaggio's plan to persuade consumers to buy a scooter as an alternative to travelling by bus or Tube.
Clear Channel's marketing director Yvonne O'Brien said: "As far as we are concerned the campaign is about the fact that scooters are exempt from congestion charging. Our understanding is that the ads are anti-car and not anti-public transport."
Piaggio marketing director Costantino Sambuy said that Piaggio had originally sought a small ad agency, but that Bates was appointed due to the freshness of its ideas.
He stressed that he wants to broaden the brand's appeal and target groups such as teachers and nurses.
Media will be handled by Carat. There is no creative incumbent, although Piaggio recently used Anderson Hearn Keene to handle its below-the-line business.
Piaggio has three brands: Piaggio, Gilera and Vespa. Sales have risen from 600 in 1993 to 30,000 in 2001.