By Nick Assinder
Political correspondent, BBC News website
For the past few years, Europe has been the issue that dared not speak its name in the Tory party and which Labour was happy to let lie.
It had proved hugely divisive for the Conservatives, helping to bring down Margaret Thatcher and fatally undermining John Major.
Mr Cameron wants a flexible Europe
And Labour was happy to keep a lid on it after rows between Gordon Brown and Tony Blair over membership of the single currency - the chancellor won and we stayed out - and the fact there are deep divisions on their own benches.
The Tory leader is now trying to change that with his speech in Brussels designed to turn the issue from a destructive to a positive force within his party and offer something distinctive from Labour.
Like Mr Blair, Mr Cameron believes the widening of Europe, with the inclusion of new eastern states, has presented an opportunity to drive a new agenda in the EU.
That is, to move it away from the "deepening" agenda, led by France and Germany, which has, critics claim, focused on strengthening the EU's institutions and centralising more power in the Brussels-based Commission.
Mr Cameron pledged to work with other states to introduce "flexibility" into the EU and demand the repatriation of significant powers.
But it is also worth noting that there is no mention in his speech of the controversial Tory policy, at the 2005 general election, of attempting to re-negotiate existing EU treaties to achieve greater flexibility.
Mr Cameron is, rather, creating a European Reform Commission with the task of finding a way of making existing EU laws reversible - so responsibilities could be returned to nation states.
That is a significant new policy that marks out clear territory for the party and its EU allies.
But, in many other ways, the agenda the two British leaders want to pursue are nearly identical.
They both put globalisation, poverty and climate change at the top of their concerns.
That has led Europe minister Geoff Hoon to claim Mr Cameron is stealing the government's clothes.
"I'm not quite sure which horse Mr Cameron is riding at the moment: is he Eurosceptic or is he changing horses to become more sympathetic to the Government's EU programme?" he said.
Mr Cameron sees an opportunity in expanded EU
And that is still Mr Cameron's dilemma. He desperately needs to settle the Europe issue on his own benches without sparking a fresh outbreak of civil war, while not playing into the hands of those, like UKIP and some on his own side, who want Britain to withdraw from the EU.
UKIP has proved it can chime with a public mood and attract disgruntled Tory votes for its policy, and that could prove seriously harmful to the Tories in the event of a closely fought general election.
But any attempt to adopt a similar approach by Mr Cameron might delight the hardliners on his own side, but he believes it would also risk isolating the Tories within Europe. And, in any case, the party does not believe in withdrawal.
Mr Cameron has already struggled with the policy he announced after the last election of taking the Tories out of the European People's Party - the centre-right grouping in the European Parliament.
That was designed to satisfy the Eurosceptics on his own benches, but proved a difficult and controversial move.
It ended with him creating the new Movement for European Reform last year with the Tory's sister party in the Czech Republic, the ODS. He claims it is now attracting interest from 14 other states.
The aim is to forge a new alliance behind exactly that new agenda, centred on the "three Gs", as Mr Cameron called them, of globalisation, global warming and global poverty.
Mr Blair would probably disagree with little in that programme and even Mr Cameron seems to be saying that the major difference between him and the prime minister is the will to stand firm against opponents within the Union.
He points specifically to the EU Constitution, abandoned after votes against in France and Holland, but being revived in one form or another by the current German presidency of the EU.
Mr Blair, he claims, first opposed it then caved in, then opposed a referendum on it, then agreed to hold one.
Only the Tories, he claims, would be clear in opposing any new constitution and giving voters a referendum if one was proposed.