If you want to raise a breach of privilege or a contempt, you should write to the Speaker. You should not raise it in the House—for example on a point of order. The Speaker will reply saying whether the matter will be treated as a matter of privilege and therefore given priority over other business set down for debate in the Chamber. If the Speaker decides to treat it as a matter of privilege, this will be announced to the House.
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 the case of 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.