David Cameron will pledge tomorrow to work with like-minded politicians to create a new European Union — one that he thinks will work for Britain and the world rather than immerse itself in distractions such as the constitution.

In one of his most important speeches since becoming Tory leader, Mr Cameron will signal the start of a new engagement by his party with Europe, reforming it from the inside so that it moves from uniformity to diversity and from being an inward-facing bureaucracy to an outward-facing association of states. It would be one which devotes its energies to matters such as global warming, world poverty and creating a dynamic economy.

Along with Mirek Topolanek, the Czech Prime Minister and leader of the ODS (civic democrats), Mr Cameron will speak at the first conference of the new Movement for European Reform, founded last year when the Conservatives said they would pull out of the European People’s Party after the 2009 Euro elections and start a new political grouping. The address will mark Mr Cameron’s attempt to get his party to start talking about Europe again but without becoming embroiled with sovereignty.

An aid said: “We have not been able to speak about Europe much because in the past we have always split over it. Now we want to be pointing the way towards where Europe should be going and saying that we will change it.”

The speech will be a clear signal that Mr Cameron will not take his party out of Europe and also a message to supporters who are considering deserting to UKIP that he will try to change the EU.

His speech comes before the signing of the Berlin declaration later this month, reaffirming the principle of unity in Europe at the 50th anniversary of the Treaty of Rome.

He will say: “This is a moment for us to reflect on where the EU is — and where it needs to be.” A visitor from Mars, witnessing the signing of the declaration, would take a close look of the inner workings of the EU and observe earnest discussions about reviving constitutions, transfers of competence, relative voting weights and other distractions.

But the intelligent Martian would say the EU should be focusing on the economic challenges of globalisation and the urgent need to reform European economies so that it could maintain its prosperity. It should also concentrate on the challenge of climate change and the need for swift action at all levels to slow the rate of global warming. And it should be absorbed by the moral and security challenge of global poverty.

“Every night, some hundreds of Africans board boats and rafts to sail to Europe. They risk death at sea in order to work in menial jobs, illegally, far from home, in an often hostile and alien culture. They do this because Africa is in a wretched state.

“This demands action for its own sake, but for our sake too we have to address the state of Africa if we are to preserve our security in the face of unstable regimes to our south.”

Tomorrow’s meeting in Brussels will be attended by other leaders, academics, business people and citizens. Mr Cameron will say he hopes it will mark a new beginning for all countries and the beginning of a process that will fundamentally change the EU.

He will say: “We want to work together with the peoples and parties of Europe who share our vision, to create a new union, a new union based not on uniformity and compulsion, but on diversity and voluntary cooperation of independent nation states. That is the vision we are working towards.”

Mr Cameron will say that his three priorities reinforce each other. “It is only by responding to the challenges of global competition and by opening up our economies to free trade that we will fight poverty in Africa. Ultimately it is enterprise, not aid that will save the developing world.

“In the same way, it is only by liberalising our economy that we will develop the technologies for energy security, the innovations that will reduce our dependence on foreign oil and gas. It is by finding sustainable ways of powering industries that we will hand on a prosperous nation to our grandchildren.”

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