You must provide proof of language for the primary applicant for Federal Skilled Worker. Always. No exceptions even if you are English and lived in England all your life (as we had, but we still had to provide proof of language).
Please note that although IELTS is the most common proof of English language, it can be from any agency approved by CIC. Currently I believe the only other agency approved is CELPIP: Canadian English Language Proficiency Index Program.
You can alternatively provide TEF results as proof of French competency as primary language.
More information can be found here:
http://www.cic.gc.ca/english/immigrate/skilled/language-testing.asp
Wayne.