Cameron EU speech: Should UK turn its back on Brussels?
23 January 2013 Last updated at 08:16 GMT
More than 50% of the goods and services produced by British firms are exported to Europe, so the impact on trade would be a key concern if Britain was to leave the EU.
Mr Cameron wants to renegotiate the UK's relationship with the EU before asking people to vote in an in/out referendum.
Jenny Hill has been to Berlin to find out if people there think Britain should turn its back on Brussels.