The IRL scale is the official level description of language proficiency. The levels are: Native or bilingual proficieny, full professional proficiency, professional working proficiency, limited working proficiency, and elementary proficiency. But I would narrow this down to fluent, proficient, and basic skill.
Fluent: This one is obvious, you speak the language at a professional or native level. You could perform any task required in that language.
Proficient: You are confident in your abilities to perform many tasks in the language. The level of your proficiency depends.
Basic: You have some knowledge and can perform simple tasks such a basic translation.
So in your case, I would say 'Fluent in spoken English, full professional proficiency in reading and writing.'
See here for a full description of each level: http://en.wikipedia.org/wiki/ILR_scale
Hope this helps!
ALSO, if you're planning on working in an English speaking country, I recommend taking the TOEFL and putting your score on your CV.