It is the first past the post system that makes a mockery of our electoral system, not tactical voting. I would love to vote Green in my area, but a Lib Dem vote has the chance of keeping out the Tories. People only feel the need to vote tactically because they feel that it is the only way to make their votes count. The most important issues to me are climate change and electoral reform. I will vote for the party in my area which is most likely to make that happen. The Tories place such little priority on climate change that they did not even state by how much they will cut emmissions over the next decade and ranked it 19th on a list of 19 important issues.
Interestingly, Bosworth does not appear on any of the lists. This is a Tory held constituency and a Tory/Lab marginal at the last general. However at last summers local elections the results were Tory 42%, Lib Dem 35%, Lab 11% suggesting that if the obviously dissolusioned Labour voters vote Lib Dem here, we could clear out another Tory.
If you are considering voting tactically, it is worth taking any recent local election results into account because there have been some big swings, which are not well portrayed by comparing the results of the 2005 general alone.