The Cabinet minister will say EU membership gives the UK access to the world's largest trading bloc worth £11 trillion and the Government is committed to growing existing trade negotiations.
Cable, speaking at an event run by pro-EU cross-party group British Influence, is expected to say: "Through successful trade negotiations we are opening up new markets for British companies to grow, as well as improving existing ones.
"We are currently negotiating a free trade agreement between Europe and India and will start formal discussions with the US - the biggest prize of all - very shortly.
"Let's be clear: leaving the EU is neither a good nor a realistic economic option for this country."
Supporters of British Influence include former Labour Party leader Lord Kinnock, former Labour cabinet minister and European Commissioner for Trade Lord Mandelson and current MP and former Conservative cabinet minister Sir Malcolm Rifkind.