The euro-sceptic UK Independence Party could become "the first force" in next year's European elections, the President of the European Commission said today.
Jose Manuel Barroso said that the increasingly anti-European stance taken by the Conservatives could help Nigel Farage's Ukip beat them in the May 2014 polls, as voters will "between the original and the copy... prefer the original".
Mr Barroso's comments came as he answered questions in the European Parliament following his State of the Union speech, in which he appeared to warn that critics of the EU who want to "roll back our integration" risk taking the continent back to the divisions and warfare of the early part of the 20th century.
He made no mention of Prime Minister David Cameron's promise to renegotiate UK membership and hold a referendum on whether Britain should stay in the EU after the 2015 general election. But responding to questions from the leader of Conservative MEPs Martin Callanan, Mr Barroso said: "I think increasingly your party and your group is looking like Ukip and the eurosceptic, anti-European group.
"I start to have some doubts that you are going to be elected yourself in Britain, if it's not going to be Ukip as the first force in British elections, because when it comes to being against Europe, the people - between the original and the copy - they prefer the original. That is why they are going to vote for Mr Farage and not Mr Callanan.
"If those forces that are pro-Europe - or even those that are not really pro-Europe but constructive - have the same speech and the same political attitude to the anti-Europeans, the euro-sceptics, the populists, they will win the next election."
In his speech, Mr Barroso hailed European integration as "the valid answer" to the wars of the 20th century.
"Next year, it will be one century after the start of the First World War. A war that tore Europe apart, from Sarajevo to the Somme. We must never take peace for granted. We need to recall that it is because of Europe that former enemies now sit around the same table and work together...
"Let me say this to all those who rejoice in Europe's difficulties and who want to roll back our integration and go back to isolation: the pre-integrated Europe of the divisions, the war, the trenches, is not what people desire and deserve. The European continent has never in its history known such a long period of peace as since the creation of the European Community. It is our duty to preserve it and deepen it."
Speaking after the debate, Mr Farage said: "It is utter arrogance that this man, who has overseen rioting in Greece, who has impoverished hundreds of thousands across the European Union by putting erroneous ideology ahead of common sense and democracy, somehow believes that his self-interested megalomaniac supra-national undemocratic organisation is the bringer of peace in Europe.
"Are they that blind as to fail to understand why the problems of Europe were caused in the past? The accountability of those serving in politics, the recourse to public opinion and the sympathy with national cultures and identities are what are key to maintaining harmony in any nation state. The EU have proven time and again they wish to sweep such considerations under the carpet in favour of promoting a self-serving power structure.
"Far from the peacekeepers, they will be proven the warmongers of this century by denying the people of Europe a voice and an identity."
A Conservative spokesman said: 'We disagree strongly with the President of the Commission.
'As the PM has said, support for Britain's EU membership is wafer thin. The EU needs fundamental change. This underlines why we need a strong result at next year's European elections for David Cameron and the Conservatives - to show Britain's absolute determination to back the PM's plan to reform the EU and give people a referendum on our membership. If Ukip do well, Brussels will ignore the outcome.
"Ukip are all talk when it comes to the EU. Only Conservatives will deliver change and a referendum."
Asked about Mr Barroso's comments, Prime Minister David Cameron's official spokesman said: "The case that the Prime Minister has been making is a forward-looking one, not one that looks to the past.
"The point is that the questions which are facing individual countries in the EU - how do we make our economies more competitive and how we strengthen our relationships with emerging economies - these are forward looking questions."
He added: "Rather than trying to second guess what the British electorate might come out with, the right thing to do is to focus on the need for fundamental change and a flexible, adaptable, open EU."