Cameron will say in a long-awaited speech this morning he wants to renegotiate the terms of Britain's membership and then put it to the public.
The pledge will form part of the conservative party's manifesto heading into the next election in two years time.
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But many have expressed concern that the possibility of a referendum could isolate Britain from the EU.
Sky's Chief Political Correspondent, Jon Craig says he's likely to address these concerns in his speech: