The phrase "denial stage" refers to a period of time when someone is refusing to accept or believe a difficult truth or situation, usually as a way to protect themselves from the emotional pain that comes with it. Full definition
Not accepting the break up has occurred by prolonging the separation is a common denial stage of the end of a relationship. (eharmony.co.uk)
As for all you «Not obsessed with UKIP = Denial stage» believers out there, denial is believeing the bilge Camerloon wrote in the ST yesterday, about EU reform being possible without leaving it (or at least credibly threatening to). (conservativehome.blogs.com)