If the Netherlands rejects the EU treaty with Ukraine at next month’s referendum it will have disastrous consequences for Europe as a whole, chairman Jean-Claude Juncker said during a speech in The Hague on Thursday.

Juncker made the comments while giving the annual Schmelzer lecture which is organised by the Christian Democratic party.

A ‘no’ vote in the Netherlands would destabilise Europe and that would be a very serious matter, Juncker said. The treaty does not mean Ukraine will be admitted to the EU, he said. ‘We have gone too quickly in the past,’ he said. ‘We will not make the same mistake again.’

The Dutch should think carefully about how they vote, he said. ‘People should ask themselves, if everyone votes the way I do, what would the impact be on Europe?’ he said.

The European Commission chairman gave a similar warning in an interview with the NRC in January.