If you wish to complain about a breach of privilege or a contempt, you should write to the Speaker. The Speaker will reply saying whether the matter will be treated as a matter of privilege. Both your letter and the reply should be kept private. If the Speaker decides to treat it as a matter of privilege, this will be announced to the House, together with the time when the matter will be considered. It will have priority over any other business scheduled for debate at that time.
You can then table a motion, through the Table Office, which will appear on the Order Paper for the next day, before the other main business the House is considering. Such motions normally refer the matter to the Committee of Privileges for investigation. The Committee will report back and recommend what, if any action, the House should take.
In a select committee report, or draft report, that has been leaked, the select committee carries out its own investigation to try to establish the source of the leak. The committee decides whether the leak constitutes a substantial interference and if it does, informs the Liaison Committee (made up of the chairs of all select committees). Taking into account the views of the Liaison Committee, the select committee makes a special report to the House and the matter is then automatically referred to the Committee of Privileges.