Should renegotiation fail Britain should leave the EU?

In a word No – but let’s be under no illusion this process which David Cameron has embarked upon it is purely to try and keep the Conservative Party together.
However, it could lead to the Britain leaving the EU. This would have massive negative economic consequences for the UK and would lead to a drastic reduction in our ability effect matters in Europe. European matters that will affect us whether we are in the EU or not.
However, it is not possible to consider the answer to question of this debate without first considering, why does the EU exist in the first place?
Since the Second World War one of the greatest achievements has been the way Europe has come together to improve the lives of people across the continent. Countries that had previously spend the first half of the 20th Century fighting and killing each other spent the second half of the 20th Century trying to work together and help each other.
The main driver of this has been the European Union, which started out as European Coal & Steel Community in 1952. The reasoning behind the EU follows the philosophy of the early 19 Century French economist Frederic Bastiat who said:-

And it follows the vision of our own Winston Churchill who speaking in Zurich on 19th September 1946 said:-

And he went on:-

Now I believe the role of a national government is not simply to pursue a narrow self-interest in all matters but to play its part helping build up the wider international community. We live in a very interconnected world, problems in one part of the world quickly translate themselves into worldwide issues. To help make the world we live in a better place we cannot do this on our own. We must work with others to achieve this goal and that must mean starting in our own backyard with our European neighbours.
For me the preamble to the Liberal Democrat constitution sums it up well when it says:-

Since 1952 in Europe we have developed a way of working together that is based on shared principles of democracy and universal human rights.

This way of working together means that:-

The purpose of staying within this EU framework is not to create a European super-state or simply a free trade association but to work with other countries to build an equitable, peaceful and prosperous international order.
That is the purpose, which we in Britain must focus ourselves on – not leaving the EU let other countries try to achieve this purpose without us.
For it is in achieving that purpose that all in Europe will ultimately benefit including us.
Leaving would only serve damage Britain and the rest of Europe.
Finally as Churchill also said in his 1946 speech: