It’s a long-standing rule of clear writing that we prefer the active voice, an authority no less than George Orwell included it in his seminal essay, Politics and the English Language.
So can we ever use passive?
Well, the passive voice is useful in scientific and academic writing when our focus is not on the subject or ‘doer’ of a particular action, but on the action itself or what is being examined.
The use of the passive voice makes perfectly good sense in this example:
652 additional procedures were performed (by medical staff) in southern region hospitals in the six months to 30 June 2014.
Why? In this instance, the use of the passive voice results in the most important information. ‘652 medical procedures’, being placed at the beginning of the sentence. And so it’s to be preferred over the active voice alternative:
Medical staff performed 652 additional procedures in southern region hospitals in the six months to 30 June 2014.
The lesson? Passive and active can both work but clarity rules.