Electoral Reform Society has been looking at what the House of Commons might have looked like if alternative systems of voting had been in place. Their simulation results offer a rough indication by way of illustration, indicating the extent to which a different system might have produced a different result - see here for more detail.
First Past the Post: Conservative 307; Labour 258 and Liberal Democrat 57
Alternative Vote: Conservative 281; Labour 262 and Liberal Democrat 79
Alternative Vote + Conservative 275; Labour 234 and Liberal Democrat 110
Single Transferable Vote (STV) Conservative 246; Labour 207 and Liberal Democrat 162
Clearly, FPTP delivered the best possible outcome for the Conservatives since all the other systems would have given them fewer seats. AV would have given Labour a slightly better result than they achieved under FPTP. STV would give the Liberal Democrats the best result. FPTP produced a hung parliament and all the other systems would have done so as well. It is argued that FPTP produces strong "single-party" government though, on this occasion, it has not done so. In fact, as in 1997, FPTP can hand a single party such an enormous majority that the executive is more or less able to do what it pleases without thorough parliamentary scrutiny. Any system other than FPTP will undoubtedly produce hung parliaments far more often and that will necessitate more dealing between parties in the formation of a workable government.
Gordon Brown announced that he would stand down as Prime Minister - see The Guardian 10th May.