Dear Sunny,
CIC doesn't compel u to take IELTS. They ONLY have a scoring system for Language capabilities. One may safely choose to ignore it, at a risk of scoring less for those points, if u think ur total points shall be enough. All the CIC wants is SOME proof. It might be by way of IELTS (or CELPIP) OR A 'Written Evidence'.
However, the Written Evidence is NOT CONCLUSIVE. You are then at the mercy of the VO. Note CICs Own Words:
/Quote/
"If you believe that you can clearly demonstrate your level of proficiency through a written submission, follow the instructions in the table below... CIC strongly advises that you ONLY CHOOSE this option if your first language is English or French (READ MOTHER TONGUE)... Note: Test results will be used as conclusive evidence of your language proficiency"...
/Unquote/
The bottomline is, if one thinks he/she can garner enough points thru the other 'selection criterions', he/she can ignore the Tests and can ONLY SUBMIT the Written Evidence. The same is well detailed in the IMM-7000, Application Guide.
But generally speaking, it is always good to take the IELTS (or CELPIP).
Regards.