Mr Clegg is expected to say at a rally in Essex: "Ukip and others have been allowed to peddle their myths unchallenged for decades, claiming all of our problems would magically disappear if the UK just left the EU.
"But it's a dangerous fantasy. It's the surest way to jeopardise jobs, risk our fragile economic recovery, and it will leave Britain alone and diminished in the world."
The Liberal Democrat leader will claim every gain made by his opponents on May 22 will represent another step closer to the European Union exit door.
After the Tory and Labour leaders skipped recent TV debates with Ukip leader Nigel Farage, Mr Clegg will say only his party can stand up for Britain.
He will say: "If not us, who? The Labour Party? The Conservatives?
"Where are they? What are they doing to stop the populists and the xenophobes? Nothing.
"Ed Miliband and David Cameron are now officially Missing in Action - saying the bare minimum in this debate because they are too scared of losing votes to Nigel Farage, because they're so desperate to cover up the deep divisions in their own camps."
Jobs, crime prevention, climate change and foreign policy are all key reasons for Britain to stay part of Europe, Mr Clegg will claim.
Mr Clegg's rally with activists and supporters will be followed by a town hall-style public question-and-answer session.
Mr Farage has denied claims a major Ukip poster campaign ahead of the elections is racist by focusing on immigration.
Elections for the British members of the European Parliament are taking place on Thursday May 22, with results from across the European Union due to be announced on May 25.