It is difficult to respond since your question is more complex than it appears at first sight. Written informed consent is not required in all cases - but it depends what you mean by a 'survey'. It is almost conventional that 'questionnaire' surveys do not require fully informed consent - the assumption is that you state what the survey is for and respondents can choose to participate or not. You 'should' at the very least seek oral consent by explaining what the survey is about and letting people ask further questions to enable them to make an informed decision to participate - their 'consent' is contained in their participation - if they don't like anything you ask, they simply withdraw and/or do not answer specific questions. You should look at the sections on consent in the attached sources.
It is clear from the attached that written consent may be seen by some participants as 'offensive' - hence not ethically acceptable!
I think written consent has been overused without reason. For example, i had the opportunity to see a written consent to apply a questionnaire about preferences related to dogs (races, sizes, behavior, etc) for a research. I read the questions and i really thought: it is absurd. If the questions are not related to the intimate sphere of life, if they dont imply a risk of discrimination, exclusion, etc. i think with verbal consent is enough. Buy if the questions involve the intimate sphere of the person or are related to sensitive issues, a written consent would be mandatory.