Just had a leaflet from the local Tories and here's how they get round this:
Quote:
How we use your InformationThe data you provide will be retained by the Conservative Party in accordance with the provisions of the Data Protection Act 1998 and related legislation. By providing your data to us, you are consenting to the data holders making contact with you in the future by telephone, text or other means, even though you may be registered with the Telephone Preference Service. Your data will not be sold or given to anyone not connected to the Conservative Party. If you do not want the information you give to us to be used in this way, or for us to contact you, please indicate by ticking the relevant boxes: Post _ Email _ SMS _ Phone_
Not saying we should do this, but is what you'd have to do to avoid any comebacks.