Thousands of people, myself included, have opted not to receive cold calls from image double glazing salesmen by registering with the Telephone Preference Service.

However, I wonder how many householders realise that by doing this, it also means they cannot be called by political parties. In the run-up to an election, and with all to fight for in marginal seats, there are hundreds of telephone canvassers around the country using their hotline to get out the vote, and particularly targeting those who are undecided.

While the Conservative Party is respecting these opt out choices, I wonder if other political parties are doing so as well.