Nigel Farage, leader of the UK Independence Party (UKIP), mocked European Council President Donald Tusk after the latter's maiden speech at the European Parliament in Strasbourg.
''Migration is the big problem,'' Farage complained to Tusk.
''You promised your voters that young Poles would return home but you have become the newest Polish émigré,'' he said.
''EU voters want massive reforms, and you are not the man to provide them," he claimed.
Farage, who leads the Eurosceptic Europe of Freedom and Direct Democracy (EFDD) within the European Parliament, also quipped that Tusk had won ''the European jackpot'' by getting his current job.
''You used to earn 60,000 euro a year, now it's 300,000 euro,'' Farage said.
''I know why you were chosen, you're perfect,'' the UK politician added.
''You have outdated opinions on the subject of Europe.''
Tusk said later that Farage's outburst was an example of the differences in political culture within the EU.
The former Polish prime minister was elected as European Council President on 30 August 2014, assuming the position on 1 December.