With regard to the existing text, it would be preferable in my opinion that the executive demonstrate that the fact of disclosing some detail would cause harm, injury, a prejudice. Clearly, that should be proven. It should not be left strictly to the discretion of the Prime Minister.
As to who should determine if the injury is sufficiently serious, the question is debatable. In the case of courts that issue judgments involving national security, the government tells the judge about the harm that could ensue if the information were disclosed. The judge examines this and renders a decision later. That sort of process could be helpful and should be considered. As for whether the decision should ultimately be made by the committee or by the Prime Minister as the representative of the executive, I have no firm opinion.