The defamation laws are clear; you should not say publicly (on television for example) anything about another person that could injure his/her reputation unless you can prove that what you say is true. Having said this, you are entitled to your opinion, but have to careful in the way that you express it if you are speaking or writing negatively. You have to be able to justify that opinion with hard facts. In Europe the European Convention of Human Rights defends our right to free speech. We can say or write what we like as long as it is not defamatory and cannot be proved. If you think about John Donne’s line “No man is an island” you have the problem in a nutshell. Or perhaps you would like to consider R.D Laing’s statement “My freedom ends where yours begins.”
The defamation laws seek to protect an individual against unfair slander and libel. (Slander is spoken defamation, and libel is written or spoken in public and reaches a wide audience.)
Now let’s take a look at negative reviews. You may be asked for example, to review a book written by your arch-enemy. The obvious thing to do in this case would be to decline the invitation to write the review, explaining your antipathy to the author. While it is perfectly fine for you to write a negative review of the work, as long as you can justify this and the review is written objectively, then you have not broken the law as contained in the Defamation Act of 1996. If you concentrate on why the book is not very good and can use passages from it to back up your opinion, all well and good. The problem arises if you review the author in a negative light, which is not what you were asked to do. Obviously in some cases reviewers refer to an author in reviews, but usually this is done to explain the similarities between the work of fiction and the author’s personal experiences.
Similarly you can write a negative review of a restaurant as long as it is justified by actual experiences of your and is not just a way of getting back at the owner who you happen not to have liked for a number of years.
Reviews of any kind must be written objectively, and whatever your personal feelings, you have to remove yourself from them and concentrate on what you are reviewing. Your personality should not come into it, and if you harbour negative feeling about the author or owner of a work, these should not colour your review.
A rule of thumb is not to be tempted to write a review if you feel that you cannot be absolutely objective. You don’t want to be involved in a law suit which will do nothing to enhance your reputation.