Dangerous. "The bigger the truth, the bigger the libel" is what cynical lawyers still say; it means that the closer you are to the truth about somebody, the more eager they are to sue.
The defence that the statement is true ("justification") is very difficult to run. Every relevant fact that you assert must be supported by compelling, admissible evidence, and that is hard to come by. You are on safer ground by pleading that what your opinion is, is a reasonable one to hold. So, for example, you might say that long delays in A and E smacked of incompetence, in your opinion. Where you hit difficulty is when you name an individual and say, in terms, that it is due to their incompetence alone; they will readily answer that they are not to blame, that it is a combination of factors beyond their control, or even that they are not the sole person who has displayed incompetence, and you would have great difficulty answering that.
Forget any idea that our law puts the burden of proof on the complainant in defamation. Even after recent reform, it is as though the defendant has the burden of proving his case.