On the issue of a committee of parliamentarians, yes to your questions. There should be such a committee of parliamentarians. Yes, it should have access to secret information. It is in fact a rarity now in western democracies not to have such a thing. In relation to your question about oversight, I'm prepared to say that judicial warrants are a form of oversight, but it is a limited oversight, and once the warrant walks out the door, there is not a feedback mechanism.
On March 12th, 2015. See this statement in context.