Both a radio ad and national press ad stated: "The Diploma, opening the doors to university and work".
Both claimed that the diploma provided valid entry into ‘all universities’.
Two people said that the ads were misleading as they believed Cambridge University only accepted the diplomas in one subject.
The Department for Children, Schools and Families which produced the campaign, said it had worked closely with university and admissions bodies to keep the content accurate in the ads.
It said Cambridge had said it would not accept all five of the Diplomas for admission on its degree courses.
All other universities said they would accept more than one, or all, of the Diplomas. On this point, DCSF felt the ads’ claims were justified.
The ASA noted Cambridge only accepted the Diploma in engineering, on the condition it was taken alongside A-Level physics, but did not accept the additional four Diplomas.
It also said that a small number of other universities would not accept all five Diplomas.
The watchdog concluded the ads were misleading and must not appear again or be broadcast again in their current form.