The next round of Brexit talks has been postponed by a week to "allow more time for consultation".
"All I can say is thank God we're leaving because you've learned nothing from Brexit".
Jean-Claude Juncker was speaking two days before European Union finance ministers meet to discuss plans to introduce higher taxes on digital multinationals like Google and Amazon, which stand accused of paying too little tax in Europe.
After fierce criticism from Britain over inefficiency in the EU, Juncker proposed that his role as president of the European Commission be merged with that of the European Council.
David Dingle, chairman of Maritime UK, which promotes Britain's shipping, ports, marine and business services industries, said the sector could thrive if the country got trade negotiations "right" after it leaves the European Union.
French President Emmanuel Macron has made ending this practice, which he says amounts to social dumping, a key priority.
Mr. Juncker also laid out steps to increase the bloc's security in coming months. "From the Brexit referendum, to the terrorist attacks, to slow growth and continued high unemployment in several of our member states, to the ongoing migration crisis, Europe was challenged in many ways".
Both the Greens and Liberals are demanding that the parliament pushes for the creation of a transnational list of European candidates, but the committee's chair, Polish centre-right MEP Danuta Huebner, said the legal basis is missing. The former Luxembourg premier urged deeper integration across the board, calling for more states to join the euro and the passport-free Schengen area, and proposing a single European Union chief and dedicated pan-European finance minister. For now, only 19 of the bloc's 28 members share the common currency.
Mr Juncker accused Turkey of distancing itself from the European Union and said the country would not become a member of the bloc for the "foreseeable future". The parliament plays an essential role in passing legislation together with the Council, and is the only European Union institution where it's members are directly appointed by European Union citizens. "Creativity and political will is needed to ensure that this does not happen", he added.
The foreign secretary, Boris Johnson, said it was important to make sure the UK's "commitment to European security is undiminished" after Brexit, citing collective efforts to bring Iran to the negotiating table and the united response to Russian aggression in Ukraine as areas of successful EU action in the past.
He added: "We will always regret this".
Labour wants to remain in the single market during the interim period following Brexit day, now set for March 29, 2019, while a eurosceptic group of Conservatives is pressing May to make a clean break.