Using data from The Guardian, we can see if the Lib Dems cost Labour a majority.

In how many seats did a Labour candidate lose to a Conservative? 137.

But this doesn't tell the whole story. In Clacton, even if all the 5,577 Lib Dem votes had gone to Labour, the 16,376 is still well short of the Conservative's 22,867.

So, in how many of those seats, would the Labour candidate have won if every single Lib Dem voted Labour? 92.

Conclusion

If every Lib Dem voter in a Lab/Con marginal had voted Labour, the result would be Con = 214 Lab = 350 Lib = 57

So, the Labour Party would have ~3% majority in Parliament. Only 24 seats. A majority, sure, but not a hugely useful one.

Remember, that's assuming every single Lib Dem voter in a Lab/Con constituency voted Labour.

Would you call that the Lib Dems costing Labour the election?

The Stats

This table show every Conservative won seat where Labour came 2nd. What would have happened if 100%, 75%, or 50% of the Lib Dem vote went to Labour. As some have mentioned in the comments, there is no guarantee that Lib Dem voters would automatically vote Labour. Given that support for the Lib Dems only went up 1% nationally, it's hard to credit Labour's defeat to the Lib Dems.



I'm what you would probably describe as a natural Labour voter. I'm middle class, the son of teachers, University educated, member and representative of the NUS, I'm employed by a big British company, I'm a proud union member and a home owner.  I even spoke at the TUC before Gordon Brown took the stage.

I probably won't be voting Labour in the next General Election. I say probably, because you still have a chance to win me back.

Allow me to explain.

I was a few months short of being able to vote in the 1997 general election. But I campaigned hard for you; as hard as a 17 year old can.

I was ecstatic when you won. I stayed up all night celebrating.  This was going to be the start of a bright new future. I was looking forward to voting for you as soon as possible.

Then a strange thing happened. You hit me with tuition fees. My family could just about afford it, but it felt like a small betrayal.

You introduced the minimum wage - you set it too low, but that's the compromise of politics. What hurt was keeping it artificially low for younger workers.

There were many other ups and downs - no party is perfect - but I was generally happy.

When it came to the first election, I tried really hard to vote for you - but you wouldn't let me! In every ward and constituency I have ever voted in, you've not either not fielded a candidate or had such a poor showing that I would be wasting my vote.

Your intransigence in sticking to the first past the post voting method caused me to hold my nose & vote for the Liberal Democrats; anything to keep the Tories / UKIP / BNP out.

You've stymied my attempts to vote for you! The outdated method of voting discourages new voters. This needs to be remedied. It may mean you lose some of your power - but that's democracy.

I'll skip over House of Lords reform and a lot of other issues - creationism in schools, corruption, -  all of which I'm passionate about, but they're better addressed by more eloquent bloggers. I'll  concentrate on the three points which now prevent me from voting for you.

The Iraq War

You knowingly lied to us and, in my opinion, allowed this country to become involved in War Crimes. Millions of us marched against this war and you ignored us. Then you had the temerity to say that people were disengaged with the political process! We are not disengaged with you - you have abandoned us!

ID Cards

These are symptomatic of the utter disregard with which you hold our civil liberties. They are a costly boondoggle which have no tangible benefits. Make no mistake, there are thousands of us prepared to stage mass civil disobedience - including imprisonment - to convince you to scrap this illogical and wasteful plan.

Your slavish adherence to The Daily Mail

It seems that you would gladly abandon any principle in order to get a good write-up in the gutter press. Every time they run one of their petty, bullying, coniving "campaigns" you feel the need to cave in to them. You've failed to realise that the mainstream press is rapidly becoming insignificant. Every time you give in to them, you abandon your supporters a little more.

...and breathe...

Now, obviously you're doing something right; you keep winning elections. Albeit with a smaller & smaller share each time.

But you have lost me - a natural Labour voter.  At the European Elections, I'll be voting for the Liberal Democrats.

However, it's not too late! You can still win me back.

• Grow a backbone. Stand up to your detractors. Keep your principles. When the Daily Mail has a pop at you - ignore them.
• You have a mandate from the people; act like it. Let people judge you on your record, not on the lies they read in the press.
• Give us the reforms which you started in 1997.  Make British democracy a shining beacon to the world - not a fusty, dying, inefficient relic.
• Remember that you govern at our pleasure. Keep us free, safe and happy.
• Apologise.  You've done wrong. You know it.  We're smart enough to know the difference between a course correction and a U-turn.

I'm enjoying what I see of the Lib Dems. They have smart policies and relatively uncorrupted MPs.  If you don't start addressing your problems, you'll find more and more of your natural voters abandon you.

I know you can change. Remember, while the polls for you are at rock bottom; things can only get better.

Yours etc...