David Campbell Bannerman MEP: The Conservative Party - not UKIP - offers the most realistic way out of the EU

David Campbell Bannerman has been an MEP for the East of England since 2009. Last month he defected from the UK Independence Party to the Conservatives.

It is perhaps appropriate my first article as a returned Conservative is for ConservativeHome, for I have received a genuinely warm welcome home.

Before my seven years with UKIP as Party Chairman, Deputy Leader and Head of Policy (writing the 2010 manifesto), I was a Conservative for twenty years. I served as a Government Special Adviser (Northern Ireland 1996-97), Bow Group Chairman (with Eurosceptics such as Bill Cash, Michael Howard and Dan Hannan), a Conservative councillor in Tunbridge Wells, and as a parliamentary candidate.

Having said that, I have not come home as a repentant sinner but someone who still believes in UKIP's central message: that of British withdrawal from the EU, which many Conservative members and parliamentarians believe in too, with a number lending their vote to UKIP in European elections. My official statement graciously acknowledged this, saying: "Of course, I have not always seen eye to eye with the Conservative Party on every issue. I continue to believe personally that Britain should leave the EU".

So why do I think that I am better pursuing this goal from the Conservative camp and not within UKIP?

There are essentially two ways for the UK to withdraw from the EU. The first is if a UK Government with a sufficient majority and manifesto commitment repeals the European Communities Act 1973. The second is a successful binding In/Out EU referendum which finds a majority of the British people wanting to leave, with their wishes then being enacted.

To date I have been pursuing the first option. I joined UKIP because I believed it had the chance to become a serious, credible political party which could help achieve its goal, through political influence or elected MPs working in coalition, possibly under a new voting system. UKIP would have to win Westminster MPs, by building up its support base and electing local councillors over time, and demonstrate that the EU issue was essential to domestic issues. Hence the vital role of policy.

But I have left UKIP now because I believe it has no credible plan - its sole aim now is to achieve twenty MEPs - but it is MPs, not MEPs, that will get the UK out the EU. The party is disorganised and unfocused, has dumped four years of policy work that was beginning to make UKIP relevant in domestic elections, and has now gone to war on its own MEPs.

In short, UKIP has decided it really is a single issue pressure group rather than a political party. In that decision it has let down the many decent, principled, hard-working and dedicated people in UKIP.

So what of the second option - an In/Out referendum on the EU?

I do not come to this naively. Whilst I would personally advocate an In/Out referendum, I recognise that the official Conservative position is not to have one, but I do welcome the 'referendum locks' on any further transfer of sovereignty, the Sovereignty Bill, and David Cameron's robust stance on the EU budget.

I feel though that circumstances can change rapidly, as history illustrates. Harold Wilson firmly ruled out a referendum on EEC membership in 1970, but later his shadow cabinet voted for the one that took place in 1975. Even the pro-EU Tony Blair surprised everyone by announcing a referendum on the EU constitution in 2004 saying that "the weather had changed" and in the Commons: "Let the issues be put. Let the battle be joined!".

I think a decisive factor in an In/Out referendum taking place is to what extent Europhiles as well as Eurosceptics want to resolve the issue. The Conservatives' partners in the Coalition, the Lib Dems, have publicly backed a 'real' In/Out referendum. Whilst they were decisive in opposing a UK referendum on the Lisbon Treaty, Nick Clegg said in 2008 that "it is time to give its first chance in 33 years to decide if it wants to be in or out of the EU... we have been signed up to Europe by default: two generations which have never had their say."

The Lib Dem 2010 manifesto stated that the party would call an In/Out referendum "the next time a British government signs up for fundamental change in the relationship between the UK and the EU".

Labour recently announced an opportunistic Eurosceptic stance, saying they may back Tory "No-Bailout" advocates, with the Shadow Treasury Minister commenting that the UK "had pumped in more than its fair share".

Whilst Ed Miliband is reported to be wary of going for an In/Out referendum (but is pro a Euro referendum), his Shadow Minister for Europe, Wayne David, said only in February that "the Labour Party is having a fundamental policy review and this [an In/Out referendum] is one of the things that will be considered".  Old Labour, such as Tony Benn, were often withdrawalist and Labour remain the only major party ever to have advocated withdrawal in a manifesto.

If numbers get tight then the DUP's clear position to have an In/Out referendum could be decisive. The Greens were also against a European superstate in their 2010 manifesto, and the SNP have Eurosceptic tendencies on fishing and other issues, and a consistent enthusiasm for constitutional referendums.

Public support for such a referendum is likely to grow, and politically neutral groups such as the EU Referendum Campaign and People's Pledge are having a galvanizing effect. Many supporters of such a referendum are not Eurosceptic.

For us 'outers' to win such a campaign, as both the AV and EEC referendums have illustrated, the campaign needs to start right away. I think we Eurosceptics have been too focused on pointing the negatives out about the EU (we are spoilt for choice) but really have a duty to articulate what I call a 'Positive Vision' of an alternate, independent Britain in a friendly free trading relationship with the EU.

I think the myths need to be nailed - the 'three million jobs lost' argument nonsense (the EU already has 64 free trade agreements and the UK is the EU's single largest single trading partner). The advantages of independence in terms of freedom of action (full immigration controls, restoring fishing waters to 200 miles, scrapping of the Working Time, Temporary Workers, AIFM and financial services Directives), freedom of resources (EU membership fees alone are soon to reach £60 million a day) and freedom of people (the return of democratic decisionmaking to Westminster) are all saleable.

In conclusion, I have decided with sadness that UKIP cannot achieve its stated ends as a party but retains an important role as a pressure group. I believe it is only the Conservative Party that can realistically offer a way out of the EU, through a future manifesto or through support for an In/Out referendum. Now I seek to persuade from within, not to shout from the sidelines.