Started getting these calls recently.
Called the 0845 number mentioned in other posts and asked to get my name removed from the database. Asked why I was being called if i am registered with TPS. They said that they were calling on behalf of someone else, most likely a motor insurer who had given me a quote recently. I used moneysupermarket, confused and a couple of others when I renewed my insurance last month, so had many quotes.
They were very friendly and offered to find out who they were calling on behalf of (I declined this offer - didn't want to appear willing to accept further calls).
Let's see if it works...