Parliamentary Progress and Processes

The list would of Conservative gains almost certainly have been longer, possibly producing an overall majority and a more settled European policy had Dave kept to his "cast iron" commitment on the Lisbon referendum and thereby secured the UKIP vote

In Dave's own words:-

http://www.thesun.co.uk/sol/homepage/news/eu_referendum/article273758.ece
"Today, I will give this cast-iron guarantee: If I become PM a Conservative government will hold a referendum on any EU treaty that emerges from these negotiations."

http://www.conservatives.com/News/Speeches/2009/05/David_Cameron_Fixing_Broken_Politics.aspx
"We will therefore hold a referendum on the Lisbon Treaty."

Look at the URLs in detail. In neither case is there any qualification about retreating from this commitment in the event that the Lisbon Treaty had been ratified.

The LibDems also have form. Their 2005 manifesto stated:-
"We are therefore clear in our support for the constitution, which we believe is in Britain’s interest – but ratification must be subject to a referendum of the British people."

Any Tory-LibDem concordat should therefore include commitments to referenda on (inter alia) Europe as well as electoral reform.

Following the shambles we witnessed last week this should also allow the introduction of a voting system more appropriate to the 21st century - rather than the 19th.