From what I know...
...this is roughly how it works.

To begin with, there are only a handful of companies that actually collate people's information, most call centres purchase their databases from one or other of these companies.

When you sign up to the TPS, they contact these collation companies who remove your details from their database.
This then filters down to the companies that purchase information from them next time they update/renew their databases, this process alone can take up to about 28 days.

Once that's done, you should be off the majority of cold calling lists (though some companies produce their own, which is a different matter).

However, once this is done, because the collation companies are legally required to completely remove your details from their system, if you then do something that causes them to acquire your details again (ie sign up to some sort of online competition), you will be re-added to the database as they have no list of previously-removed details to compare you to (the Data Protection Act or some such thing prevents it).
Obviously, from there, your details can then filter back down to the companies that cold call you.

So, the best form of defence is offence - you basically need to contact the TPS about once every 3 months or so, so that they will continually remind the collation companies that you do not want to be called, and that should be the most effective way of avoiding cold calls.
Of course, any that you do receive, instead of just hanging up you should inform them that you are signed up to the TPS and it avoids them calling you back.
(Pope Jamiroquai III, Thu 3 Sep 2009, 21:57, 1 reply)

Not quite right
They're required to screen their DBs against TPS regularly, so once on TPS, that should be it.

As above, as soon as you mention TPS to any outbound call centre, they'll shit themselves and drop the call instantly. It's always fun to capture their data 1st mind, particularly the outsourced ones, as being on the Information Commissioner Shitlist is very, very bad for their business.
(MartinB9999, Mon 7 Sep 2009, 11:40, closed)