The Correio da Manha poll found that 38.6% of those questioned still believe Kate and Gerry McCann were involved in their daughter's disappearance in the Algarve.
On the other hand, 30.7% thought the couple, from Rothley, Leicestershire, were completely innocent.
This compares to a poll run by the same newspaper in September last year, in which 39.9% of people interviewed thought the couple were guilty and 26.8% believed they were not to blame.