Exports to European Union countries are worth £211 billion to the British economy and help support 4.2 million UK jobs, according to analysis by an economic think tank.
The Centre for Economic and Business Research (CEBR) study of figures for 2011, the most recent full set of data available, shows that the EU's demand for goods and services from Britain has steadily increased since a similar piece of work was carried out in 1997.
The report, for the British Influence group which campaigns for the UK to remain in a reformed EU, found that income from exports to other member states was worth £3,500 per head of the population in 2011.
Within the 4.2 million jobs, an estimated 3.1 million were directly supported by exports to the European Union in 2011 and 1.1 million jobs were indirectly supported, for example through spending income earned from exporting.
The analysis found that the number of jobs associated with demand from the EU has increased from 3.7 million to 4.2 million over the period 1997-2011.
This CEBR research does not suggest that the estimated jobs would be lost if the UK were to cut ties with Brussels and it does not include an analysis of net trade, taking into account imports from the EU.
It also indicates that although the EU's demand for British goods and services from the UK has steadily increased since 1997 "as a share, EU demand has decreased as growth in demand from emerging markets has outpaced it".
"But in terms of the absolute volume of goods, the numbers have steadily increased and the EU remains the UK's single biggest trading partner by a wide margin," the report said.
The study also identified regional variations in the distribution of EU-associated jobs, from London's growth of 27% to West Midlands' fall of 6%.
The report found the value of EU exports in 2011 was 77% higher than 1997 and total exports 105% higher.
Douglas McWilliams, executive chairman of CEBR, said: "This report demonstrates the levels of UK economic activity that are associated with demand from the European Union.
"CEBR estimates this at 4.2 million jobs, or £211 billion in national income terms. Jobs are spread across UK regions, but East Midlands and West Midlands have the highest proportion of their workforces supported by demand from the EU.
"Across the economy, the manufacturing sector has most jobs linked to demand from exports to the EU but it is notable that between 1997 and 2011, the numbers of EU-supported jobs in business services have almost doubled.
"As the debate of the UK's relationship with the EU continues, I think it is important that debate understands a sizeable chunk of the UK economy is supported by demand from EU member states."
Matthew Elliott, chief executive of the eurosceptic campaign group Business for Britain, said: "The CEBR has shown that the EU remains Britain's largest export market and that is reflected in the number of jobs involved.
"However as the report recognises, the EU's share of UK exports is decreasing. More work needs to be done looking at the rising influence of markets in China, the Far East and South America and how Britain (and the EU) can maximise trade with these new economic powers.
"There is no doubting the Single Market importance, but it still levies a disproportionate burden on many British firms, especially SMEs, who would benefit from less red tape and a more global outlook from Brussels."
British Influence director Peter Wilding said: "This new research points to the continued importance of our trading relationship with the EU. It represents an effective barometer reading of the jobs and wealth generated by that ongoing and vibrant trading relationship.
"It would be absurd to claim that all that would evaporate overnight if we were to withdraw from the EU. But it would surely be an act of madness to jeopardise economic reality based on facts in favour of little more than a pipe dream of alternative trading relationships articulated by those who propose that we should walk away."
TUC general secretary Frances O'Grady said: "One in seven British jobs already depend on trade with the rest of the EU, and these four million jobs tend to be more highly skilled and better paid than most.
"Jobs in the Midlands and Yorkshire are even more reliant on exports to Europe than jobs in other parts of the UK. The recovery won't deliver for large parts of the country if the needs of the regions are ignored.
"Trade with Europe is vital to the British economy and to the living standards of people at work. Britain's membership of the EU needs to work for Britain, and for working people that means the right to good jobs, better training and higher pay."