A fully fledged federal Europe may seem like "political science fiction" today but will soon become reality for all European Union countries whether inside or outside the euro, Jose Manuel Barroso has said.
"This is about the economic and monetary union but for the EU as a whole," he said.
"The commission will, therefore, set out its views and explicit ideas for treaty change in order for them to be debated before the European elections."
"We want to put all the elements on the table, in a clear and consistent way, even if some of them may sound like political science fiction today. They will be reality in a few years' time."
Mr Barroso's announcement that he will set out plans for a European federation next spring, before elections to the European Parliament in May 2014, will further deepen Conservative divisions over the EU.
The intervention will add weight to the argument made by Lord Lawson, and other anti-EU Tories, that it is pointless to try and improve Britain's membership terms when the dynamic, set by the eurozone, is towards a fully-fledged federal Europe.
The commission president's argument is that as the eurozone adopts federalist structures on fiscal and economic policy, supported by Britain as necessary for financial stability, there will also be a need for political structures that will fundamentally change the way the EU works.
"Further economic integration would transcend the limits of the intergovernmental method of running the EU and the eurozone in particular," Mr Barroso said.
Writing in The Times today, Lord Lawson, the former Chancellor, has reignited the Tory debate on Europe by calling for exit from the EU because developments in the eurozone have changed Europe's politifal structures, an argument that mirrors Mr Barroso's case for a new federal or constitutional treaty.
"The heart of the matter is that the very nature of the EU, and of this country's relationship with it, has fundamentally changed after the coming into being of the European monetary union and the creation of the eurozone, of which - quite rightly - we are not a part," Lord Lawson wrote.
Proposals for an EU "political union", with budget policies set in Brussels and an elected president of Europe, will derail David Cameron's attempts to negotiate a new settlement for Britain, culminating in an "in or out" referendum in 2017.
In stark contrast to the Prime Minister's call for Britain to regain sovereignty from Brussels, Mr Barroso has called on all European leaders to accept that political union is inevitable in order to confront outright opposition to the EU, such as that from the UK Independence Party.
"This is why I believe the mainstream forces in European politics must seize the initiative, should leave their comfort zone to welcome and embrace this debate, rather than relinquish the momentum to eurosceptic or europhobic forces," he said.
"If you believe in the democratic resilience of Europe, if you take Europe's citizens seriously, you have to fight with rational arguments and unwavering convictions - and be convinced, as I am personally, that these will win the debate for us in the end."