Mother has been asked to create an integrated campaign for the new ITV2 drama series Belle De Jour, which stars Billie Piper.
Mother will work with the broadcaster's in-house agency ITV Creative and its newly appointed digital agency Dare, to develop an integrated campaign for the new drama, which airs this autumn.
The agency won the one-off project without a pitch.
However, ITV said the appointment did not affect its relationship with M&C Saatchi, which will continue to work on ITV1 and ITV Consumer, including the upcoming launch of itv.com.
The appointment follows the promotion of David Pemsel, the group marketing director of ITV, who replaced Clare Salmon in January. Salmon appointed M&C Saatchi to handle ITV's above-the-line advertising account when she stepped into the role in 2005.
Stef Calcraft, a partner at Mother, said: "A fresh creative confidence and ambition is palpable everywhere at ITV. We are delighted to be involved in an assignment, which has such potential to break new ground."
Mother has strong credentials in building and marketing TV brands, the agency launched Channel Five back in 1997 and was also behind ITV Digital's much-loved "monkey" campaign.