Why do British mps resort to calling a loosing election down to a protest vote?

It seems that in England it becoming more and more often that mp's call a loss or a under performance down to the public using there votes as a protest for change? How undemocratic is that how dare they even suggest that! That is by far a big example of how little the politicians in the united kingdom think of the "general" public.

Also it seems very much as though the politicians believe that people cannot vote for who they want anymore.

Idiots! who are we meant to vote for then? if all three of the major parts in England are practically the same?