It is a tragedy that campaigning in what looks like a very narrow vote in a referendum to change the Turkish constitution has caused what may be lasting damage to Turkey’s relations with Europe. A stream of outrageous comments from President Recep Tayyip Erdogan directed at the Dutch and Germans may play well with his xenophobic electoral base, but have caused deep resentment in Europe that will not be easily forgotten.

If Turkey’s April referendum votes in favour, the presidency would be vastly empowered, and the existing checks and balances would be weakened.

The tight polls have led Erdogan’s supporters in favour of the change to ignore Article 94/A of Turkey’s general election law, which explicitly bans campaigning abroad, to call for rallies where there are large Turkish populations. Permission for these controversial gatherings was refused in Germany and the Netherlands leading to Erdogan calling them both Nazis.

It is hard to describe how deeply insulting it is to call a German a Nazi. The appalling episode of Adolf Hitler and the fascist National Socialist Party dragged Germany and the rest of Europe to the hell of the Second World War. The country of Goethe and Schiller, of Hayden and Beethoven, which has contributed so much to European culture and liberal thought, was overwhelmed by a ghastly horror.

In the 70 years since the end of the war, modern Germany has recovered and played a vital part in the vast exercise in international tolerance and peace that is the European Union.

The Dutch endured a grim period of Nazi occupation, including the dreadful task of rebuilding their nation after the war when resistance fighters and collaborators had to learn to work together. Then Erdogan further insulted both nations by saying that Germany was harbouring terrorists and accused the Netherlands of an armed forces failure to stop the 1995 massacre in Srebrenica, which was grossly unfair given their lack of forces and their United Nations orders.

Whether Turkey votes in favour of an autocratic presidency or remains as it is, its government still needs good relations with Europe. The increasingly erratic Erdogan hopes that whipping up anti-foreign Turks will give him a few more votes in the referendum, but afterwards Turkey will suffer from his folly. Neither side will want to completely sever relations, but given the current maelstrom of invective, no-one will want to expose themselves.