By Anushka Asthana, Political Correspondent
UKIP could topple the Conservatives to become the "first force" in British politics, the President of the European Commission has said.
Jose Manuel Barroso criticised the Conservative party for becoming eurosceptic, warning that voters might "prefer the original to the copy".
He made the provocative comments during his annual state of the union address.
Mr Barroso hit out at anti-Europe sentiment, arguing it would drive the continent back to a time in which it was riven by conflict.
He said: "Let me say to those, including some in this House, who rejoice in Europe's difficulties and 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."
He said it was the commission's "duty" to preserve and deepen the EU.
After his speech, Mr Barroso took part in a debate.
Martin Callanan, the leader of the European Conservative group, said the commission was representing the "vested interests of the European District in Brussels not the people of Europe".
Nigel Farage's party is a formidable force, Mr Barroso suggestsMr Barroso hit back: "I think increasingly your party and your group is looking like UKIP."
But Nigel Farage's anti-Europe party had a better chance of wooing the British electorate, he added.
He said: "Because when it comes to being against Europe people prefer the original to the copy.
"That is probably why they are going to vote more for Mr Farage than Mr Callanan."
He said he did not make the comments with any "satisfaction".
Mr Callanan said it was a "bit rich" for an unelected head of the European Commission to give electoral advice.
A source close to Prime Minister David Cameron said Mr Barroso should "respect the views of the governing party elected by the people of Britain".
The source added: "Of course it would be more convenient to the Brussels elite to have other parties they think they can ignore.
"However, the Prime Minister will continue to stand up for the British people fighting to ensure they get the best deal in Europe and have a say on it in a referendum by 2017."
Mr Farage said Mr Barroso was right to say that the only real debate is whether Britain remains in the EU and "not the unrealistic promises by David Cameron".