In his address to the European Studies Centre the Liberal Democrat leader, whose party supports closer integration with the EU, will call the grouping of 28 different states “imperfect ... but still the most successful example of international cooperation in modern history”.
Clegg has seen his party’s poll ratings hit hard as a result of his stance on Europe but in a speech which refuses to waver he is expected to play up the British influence on the EU in its current form, including Conservative Margaret Thatcher’s support.
He will also paint Ukip and the Conservatives as “isolationists” acting against the nation’s best interest.
The Lib Dems are expected to achieve under 10 per cent of votes in the EU elections. The result will be announced on Sunday at 10pm.