1. a person whose advice is unreliable, questionable, or of uncertain value; someone whose judgment or expertise is questionable
He proved to be a doubtful advisor in matters of finance, often giving contradictory suggestions.
Ele se mostrou um conselheiro duvidoso em questões financeiras, frequentemente dando sugestões contraditórias.
2. a person whose motives or competence are unclear or suspect
The committee dismissed him as a doubtful advisor due to his lack of credentials.
O comitê o descartou como um conselheiro duvidoso devido à falta de credenciais.