It's a matter of opinion, but I feel that Wikipedia gives a fair summary of the situation:
According to Debrett's Correct Form the English title "Councillor" (often shortened to ‘Cllr’) applies only to elected members of city, borough or district councils. However, there is no legal basis for this restriction and in practice the title is applied to all councillors at all levels of local government. Where necessary, parish and county councillors are differentiated by the use of a fuller title such as "town councillor" or "county councillor". The title precedes the holder's rank or other title, as in Cllr Dr Jenny Smith or Cllr Sir Ricky Taing, and for women it precedes their title of marital status, as in Cllr Mrs Joan Smith. Youth councillors are solely known as Youth Councillors.
You can read the full entry at https://en.wikipedia.org/wiki/Councillor.