Electoral System biased?

I've seen a few comments in the right-wing side of the blogosphere complaining that the UK political system is biased in favour of the Labour Party.

It's certainly not deliberately biased in favour of the Labour Party, even though Labour were more efficient than the Tories in the mid 90s round of redistricting, the effect of that was not large, and in any case the political parties are not able to gerrymander seats in the way that US parties can. So it's not biased delibrately.

However the FPTP electoral system we have here, combined with a two and a half party system does lead to the potential of odd effects happening. But it doesn't mean that the system in itself is biased to one side or the other.

Say there were 3 major parties with roughly equal support, We'll call them Party A, Party B and Party C. Parties A and B both dislike Party C far more than they dislike each other and they agree to only stand 1 candidate against Party C in each constituency. The effect is just a stronger version of the effect of Labour ignoring a couple of hundred constituencies every election for the Lib Dems to have a free run at.

Back to the example, this did happen in 1931, and the Party C (Labour) got only 52 seats despite getting 30.6% of the vote whereas the National Coalition got 554 seats. Even the National Liberals (part of the Coalition, later merged with the Tories) got 37 seats with less than 4% of the vote. (Source David Boothroyd)

The effect was against Labour then, as it was when Labour outpolled the Tories 48.8% to 44.3% and still won less seats in 1951, but it was against the Tories in Feb 1974. when they won more votes but less seats than Labour.

But it's the same system, the system can't be biased if it favours different parties at different times. It's just that FPTP is unstable in multiparty situations.