Mandatory Transparency Register for Lobbyists

Citizens of the European Union expect EU decision making to be as open as possible. Following this thought, why do we not have a mandatory transparency register yet?

In order to make lobbying more transparent and to relieve the mistrust against professional lobbyists I call for an implementation of a mandatory registration of every lobby organisation.

Not only does this help serious, professional lobbyists to clear their image but also prevents shady lobbying strategies from interfering in European politics. A strong democracy like the European Union profits from a landscape of diverse interests and therefore has to provide sufficient mechanisms of transparency.