Brignell retired in the late 1990s from his academic career and now devotes part of his time to his interest in debunking what he asserts to be the use of poor science and false statistics common in much of today's media. In this context, he has expressed controversial opinions on many subjects. In particular, he has disputed the theory of anthropogenic global warming, November 2001 questioned the relationship between second-hand smoke and lung cancer, November 2005 and suggested that the hole in the ozone layer existed before the rise in the use of chlorofluorocarbons.

He has published two popular science books, Sorry Wrong Number and The Epidemiologists: Have They Got Scares for You!, which have been reviewed in the British press (for example,).

In mid 2005, Brignell prepared a list of over 600 links to news reports linking various contradictory phenomena to global warming. In November 2007, this list appeared on the spiked website Got a problem? Blame global warming! | spiked, then the Rush Limbaugh show , and has since been quoted in other places, eg.

Bob Carroll (author of the Skeptic's Dictionary) initially accepted Brignell's argument against the EPA. However, he changed his mind on the basis that the "scientific principle" (relative risk less than 2) that Brignell used to reject the finding was not recognized by epidemiologists. Skeptic's Dictionary Newsletter 41