David Cameron’s promise of an in-out referendum on Britain’s membership of the European Union by the end of 2017 has been described by some as a bold move.

Others complain it has created an air of uncertainty that will damage the economy as it drags on over the next few years.

Certainly the Prime Minister and Witney MP’s words have injected more urgency into the debate about whether the UK should stay or go.

We export about £150bn worth of goods to the EU and as many as 3.5m workers are in some way dependent on the single economy, so the stakes are incredibly high.

Here in Oxfordshire, one of the biggest employers is German-owned BMW and many of our most successful companies have strong trading and employment links with Europe.

Euro-sceptics claim that we could leave while still maintaining something like our current close trading links with the EU, along the lines of Iceland, Liechtenstein, Norway and Switzerland, who make up the European Free Trade Association (EFTA).

Oxford-based South-East MEP Catherine Bearder dismisses the idea that Britain could thrive under such an arrangement as “a nonsense”.

She says the BRIC countries, the emerging powerhouse economies of Brazil, Russia, India and China, want to trade with the EU, rather than setting up complicated agreements with individual European countries.

She pointed out: “The EU is still the largest market on the planet, bigger than America, bigger than everywhere else.

“Half a billion people live in the European Union. BRIC countries want to trade with us and do the trade deal with the European Union.

“If the UK was outside the EU, companies would say ‘why should I invest in the UK? I would much rather invest where the market is, where I have a free market and access to all the countries and all the consumers’.”

She warns that even if we quit the EU, we would still have to conform to EU standards and regulations in order to continue trading with it.

She added: “We would have to conform and yet we would have no voice in that decision on setting on the rules.

“We would be marginalised, it would be more expensive and we wouldn’t be able to have our voice around the table.”

Banbury-based Norbar Torque Tools won the export category at the Oxfordshire Business Awards last year and has won the Queen’s Award for Export Achievement.

It exports 75 per cent of its output and has offices in India, China, Singapore, the USA, Australia and New Zealand.

Sales and marketing director Philip Brodey is convinced Britain needs to stay a full member of the EU.

He says the EU (not including the UK) accounts for 33 per cent of sales and is integral to future growth.

Mr Brodey cites the benefits of trading with Europe as being ease of transport and no duties or trade barriers, thanks to our EU membership.

He said: “Business in the EU is easier to access than in Asia where the cost of doing business is much greater because of travelling costs, substantial duties in some countries and hotel accommodation.

“If we pulled out of Europe and did not continue to have that benefit of ease of documentation and low cost of moving goods through Europe, that would put us at a distinct disadvantage. And if doing business with the UK became more complicated for other countries because we were not part of the EU, it could put at risk several millions of pounds of business.”

Hi-tech engineering firm Oxford Instruments generates a third of its turnover through sales to Europe, with the other two thirds being evenly split between Asia and north America.

It has just invested in opening a subsidiary in Mumbai and has a director focused solely on developing trade with the BRIC countries.

But spokesman Lynn Shepherd points out it also has strong links with Europe, having acquired several companies in Germany during the past five years and at least 250 of its employees are based there.

Under EU membership rules, UK nationals can live and work in any EU country and there are around 2.2m people who take advantage of this, half of them living in Spain.

Euro MP Ms Bearder says the clamour for a referendum is growing and she believes there will be one, regardless of whether or not David Cameron wins the next election.

She said: “For me, pulling out of the EU is about as sensible as somebody in Oxfordshire saying ‘I don’t like the way Westminster is run, I think Oxfordshire should pull out of Westminster’.”

“If you don’t like what is happening, then make it work better and that is what we are doing.”