Britain will regret leaving the European Union, the President of the European Commission has warned.

Speaking in his annual State of the Union address in Strasbourg Jean-Claude Juncker said the EU would respect the will of the British people but that the bloc would “move on” from the UK’s departure.

Mr Juncker unveiled plans for a summit to be held on 30 March 2019 – the day after the UK leaves – in order to discuss the future of the bloc.

He also used the speech to spell out a major reform package for the EU: with a new push for all applicable member states to join the euro, the expansion of the borderless Schengen area to Romania and Bulgaria, as well as the merger of the presidencies of the European Commission and European Council.

He also backed the creation of a new European economics and finance minister, an idea proposed by Emmanuel Macron; as well as reforms to the European Parliament that would see some MEPs elected from European-wide lists voted on by all countries at once.

“March 29th 2019. That will be the date when the United Kingdom will leave the European Union. This will be a very sad and tragic moment in our history – we will always regret this, and I think that you will regret it soon, if I might say,” he said.

“Nonetheless we have to respect the will of the British people, but we will have to make progress, we will move on, because Brexit isn’t everything – it’s not the future of Europe.”

The Commission President, a former prime minister of Luxembourg, said he believed that the EU would continue to enlarge and “will have more than 27 member states” – though he admitted it was unlikely to do so immediately during his term as President.

In the speech, the President painted a bright picture for the future of the EU. Mr Juncker rattled off economic statistics that he said showed the EU’s economy was “bouncing back”.

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“All of this leads me to believe: the wind is back in Europe’s sails. We now have a window of opportunity but it will not stay open forever. Let us make the most of the momentum, catch the wind in our sails.”

Mr Juncker said EU growth has outstripped the US for the past two years, while unemployment in the union is at a nine-year low, with eight million jobs created during his mandate as Commission President.

“The European Commission cannot take the credit for this alone,” he added. “Though I am sure that had eight million jobs been lost, we would have taken the blame. But Europe’s institutions played their part in helping the wind change.”

Brexit: the deciders Show all 8 1 /8 Brexit: the deciders Brexit: the deciders European Union's chief Brexit negotiator, Michel Barnier Getty Brexit: the deciders French President Emmanuel Macron Getty Brexit: the deciders German Chancellor Angela Merkel Reuters Brexit: the deciders Commission President Jean-Claude Juncker EPA Brexit: the deciders The European Parliament's chief Brexit negotiator Guy Verhofstadt Getty Brexit: the deciders Britain's Prime Minister Theresa May Getty Images Brexit: the deciders Britain's Chancellor of the Exchequer, Philip Hammond PA Brexit: the deciders After the first and second appointed Brexit secretaries resigned (David Davis and Dominic Raab respectively), Stephen Barclay is currently heading up the position PA

The annual State of the Union address comes hours after the UK and EU agreed to postpone the next round of Brexit talks, which were due to take place next week.