Polish Prime Minister Donald Tusk has criticised people who derive satisfaction from the UK's decision to block a new EU treaty.
As MEPs reviewed the Polish Presidency of the Council of the European Union on 14 December 2011, Mr Tusk told the European Parliament that "we are standing at a crossroads".
He said there was a choice between taking "a community path" or the "path of national egoisms", where the EU would be seen as a burden.
On Tuesday, Ukip leader Nigel Farage prompted peals of laughter in the European Parliament as he declared to MEPs that the UK would soon leave the EU and start to regain its influence in the world "as you lot head for disaster".
Mr Tusk drew attention to what he perceived as a "disease", telling MEPs: "If you're hearing today people saying that one should revise the foundations of the EU, this is a clear sign that there is a crisis not only in our banks but also in our hearts."
Some people believed that the best way to save the euro was "to weaken, or perhaps destroy, the community".
"When I hear comments, made with satisfaction, that Britain has become an island again, that the English channel has got wider, then I don't understand why it is said with such satisfaction.
"We shouldn't show happiness that... distance is growing between member states."
Commission President José Manuel Barroso agreed: "What we need is more union, not disunion."
Mr Barroso congratulated the Polish presidency for enabling the so-called six-pack of new financial regulations to become law.
The Council of Ministers, which is one of the two arms of the EU legislature, is chaired for six months by each member state on rotation. Poland's stint comes to a close at the end of 2011, with Denmark taking over at the start of the new year.
Mr Tusk highlighted political developments achieved during his country's presidency, such as progress made on reaching a deal between member states on an EU-wide patent application system.
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on the use of simultaneous interpretations, on the European Parliament's website.