Traffic wardens don't exist any more
http://www.bbc.co.uk/news/magazine-34203585
so I assume that you're referring to the role of a 'civil enforcement officer' (or something similar).
However, as Eddie says, anyone can be dismissed from their post for almost any reason at all (or for no reason whatsoever) within their first two years in the post. The only exceptions are when the reason for dismissal fall foul of equality legislation. (e.g. the 'two year rule' doesn't apply if an employee finds out that they're homosexual or a Muslim, and then dismisses them solely because of that reason).