A vote for Brexit means a wounded David Cameron and a calamitous blow to Europe

On June 23, Britons will decide whether the United Kingdom remains part of the European Union.

The outcome of the last referendum on the issue, in 1975, was clear. More than 67 percent voted in favour of Britain becoming a full member of the then European Economic Community. Forty-one years later the stakes are higher. The result is likely to be closer.

Should the British decide to leave, and notwithstanding his electoral triumph just over a year ago, it is unlikely David Cameron could, or would want to, remain prime minister. Even a close vote for "yes" would leave him severely – perhaps terminally – weakened.

The Brexit campaign appears to have had more to do with political ego and posturing than practical policy considerations. But behind the parochial media focus on the political manoeuvring within a divided Conservative Party, with the blonde Billy Bunter-like cabaret of former London mayor Boris Johnson leading the campaign for Britain to leave, national decisions don't get much more important.

A reluctant relationship

Britain's fraught relationship with the continent has rumbled through UK politics ever since France, West Germany, Italy, Belgium, the Netherlands and Luxembourg signed the Treaty of Rome in 1957.

All post-war British prime ministers have had to negotiate more than a succession of treaties and arrangements – they have also had to survive the shifting sands of opinion within their party and the wider nation.

Even the most enthusiastic pro-European leaders, Edward Heath and Tony Blair, have had to temper their enthusiasm as they sought to strengthen and maintain British influence.

But Blair's enthusiasm for Europe was born of far more than the immediate economic arguments. During my time working at Downing Street he was advised by Roger Liddle and Sir Stephen Wall: both clear in their conviction that Britain’s best interests were served by being part of, and helping shape, European policy and regulation.

And – unlike Heath – Blair spoke fluent French.

In late 2004, prior to the UK presidency of the EU in 2005, Liddle presented a seminar to advisers and senior public servants on why making a success of Britain’s EU membership was hugely important for the national interest.

The presentation was compelling. However, even among the senior advisers and administrators in a government led by arguably the closest thing the prime ministership has had to a Euro-enthusiast, that Europe was key was rigorously questioned and even derided.

I was surprised. Whether it was reducing the risks of climate change through incentivising a low-emissions energy system, better managing agricultural land in the interests of the environment, or ensuring the standards relating to the food eaten by everyone in the country ensured both human health and assisted the British food industry, Europe and European decisions were key.

For me, Britain's relationship with Europe wasn't a question for the constitutional lawyers, academic historians and ambitious politicians. It was a daily factor in my job of providing practical – and hopefully useful – policy advice.

With few politicians keen to use their political capital making a positive case for Europe and the fraught, toxic and highly complex history of Britain’s reluctant membership of the European club, the British public has long been understandably confused.

The media like nothing more than stories of bizarre European regulations on sausage ingredients, the straightness of bananas, or the exposure of a barmaid's cleavage to the sun. And the benefits of membership are couched in technical, often economic, language that people find hard to trust and have little political resonance.

The purpose of the European Union

British membership of the European community has been a constant source of controversy. Yet whether it is what the EU spends its money on, its membership or its economic functions, much has changed in the 41 years since the first European referendum.

When the European Community was established in the 1960s, the budget was dominated by agricultural subsidies and investment. Around 90 percent went into the common agricultural policy.

When Britain joined in 1973, the figure was around 70 percent. Now, it is closer to 40 percent. So what Europe practically does increasingly means enhancing competitiveness while protecting the environment, consumer rights and human health.

At the time of the 1975 referendum, the European Community had nine members. Now there are 28; an expansion powerfully argued for by Margaret Thatcher in her 1988 Bruges speech.

The economic functions of the single market have become ever stronger – which Thatcher would also have approved of. More than 40 percent of UK exports go to, and more than 50 percent of UK imports come from, the EU. And with the free movement of labour, 10 percent of people have lived and worked in another European country; 17 percent would like to do so.

In addition to the practical developments, the European "ideal", exemplified in the preamble to the Treaty of Rome arguing for the "ever-closer union among the peoples of Europe", has lost its lustre. There just aren't any advocates to be found in Europe for it.

The Eurosceptics may still demonise them, but in their enthusiasm for European integration, French President Francois Hollande and German Chancellor Angela Merkel are far from Charles de Gaulle and Konrad Adenauer. And any fear that European bureaucrats in Brussels have any meaningful input to British education, health, fiscal and law and order policy is hard for even the popular press to amplify.

The devil you know?

Notwithstanding all the benefits of EU membership for Britain, perhaps the strongest argument for remaining is the uncertainty of the alternative.

The EU has succeeded in keeping 28 querulous, self-interested states in fragile union where policies and differences can be negotiated and resolved.

Given the links between the UK and European economies, a "leave" victory won't mean:

• no European agricultural policies vital to British farmers;
• no European environmental policies vital to British water and air quality; or
• no European employment policies vital to British businesses.

EU regulations would still apply to British goods sold in the largest single market in the world. The rules would still be there; it is just that Britain would have absented itself from helping shape them.

The polls make the outcome impossible to call. The temptation for the electorate to vote "no" and give the government and business elites a bloody nose could prove more potent than any rational argument.

With the EU no longer novel, and apparently tired and leaderless after almost 10 years of economic austerity, British withdrawal could both strengthen Eurosceptism and the far right in France and Germany. With this may come a more insular and potentially dangerous politics.

After all the intense debate and media coverage, Britons will be asked a simple question when they enter the polling booth:

• Should the United Kingdom remain a member of the European Union or leave the European Union?

It is a simple question whose answer will have complex implications well beyond the shores of the UK and the dramas of domestic British politics. The effects will surely test the endurance, or otherwise, of the whole European project.

From 2004 to 2006, Nick Rowley worked at 10 Downing Street as a policy advisor to former British Prime Minister Tony Blair. He is currently an Adjunct Professor at the University of Sydney's Sydney Democracy Network. This article was originally published on The Conversation.