What style of writing should an academic essay be? A lot of candidates, even some teachers think that IELTS Writing Task 2 is a very formal essay, but actually it’s not that formal. It's somewhere between normal spoken English, formal English and scientific, analytic English. Although many people know that we should avoid contractions (For example, instead of using “can’t”, you should write “cannot”), this is not a big issue that all candidates should focus on.
Some candidates write in an unsuitably formal style and often this kind of candidate makes many mistakes because he or she is writing above their natural sentence-making ability – that makes your essay sound really “forced”. Task 2 should not be written in the highest level of formality because, after all, candidates are encouraged to include examples from their own experience. This element of "writing personally" cannot be done at a high level of formality because writing at a high level of formality is impersonal in style. Therefore, you should not attempt to write your essay at the very highest level of formality.
On the other hand, even though the IELTS Task 2 essay should not be highly formal, neither should it contain too many examples of expressions that are mostly used in spoken rather than written English. For example, the phrase "Last but not least", I believe, is best used in spoken English situations and is not suitable for academic essays, even academic essays such as IELTS Task 2, which is not highly formal.
Don’t use those phrases in IELTS Writing Task 2:
• First and foremost
• Last but not least