This is a common question and one that we get asked a lot. Basically, it is people being poorly advised by people that know nothing about IELTS. An IELTS writing examiner explains……
Phrasal verbs are part of normal every day speech. Using them in IELTS is fine. So many people think that IELTS is a test of your academic English and should, therefore, be approached as a formal test. This is not true. It is a test of your English, nothing more.
So, can you use phrasal verbs in Task 2? Of course, you can.
Will they get you a higher Lexical Resource mark? Possibly, but you need to remember that range is just one part of the Lexical criteria. Accuracy and precision are other parts and if these are not at the same level, then you will get lower marks. I often see people use incredibly high-level vocabulary, but in the wrong context. This is an error and brings your mark down.
So, instead of focusing on phrasal verbs (or any single part of writing for that matter), you need to work on presenting clear ideas with suitable vocabulary throughout your writing. This will get you higher marks.
Good luck.
You can join our Private Facebook Group and ask IELTS examiners questions and if you need your writing evaluated by an IELTS examiner then you can order that service here.