The call for a new “register”, and for all non-Italian Roma to be expelled, has caused the first major rift between Salvini’s League and its Five Star Movement coalition partners, a week after Salvini violated humanitarian law to block a ship carrying more than 600 migrants from docking in Italy, forcing it to divert to Spain.

Luigi Di Maio, the leader of the anti-establishment M5S, called Salvini’s order “unconstitutional”. A similar census pitched by the former prime minister Silvio Berlusconi was blocked by an Italian court.

It was also lambasted by Noemi Di Segni, the president of Italy’s union of Jewish communities, who said the proposal recalled the fascist race laws of the late 1920s and 1930s. The former centre-left prime minister Paolo Gentiloni also tweeted his disgust, saying: “Yesterday the refugees, today the Roma, tomorrow guns for all.”

At first, Salvini seemed prepared to back down from his new policy – saying he was only seeking to ensure that Roma children were being adequately looked after – but in a tweet on Tuesday afternoon he promised to stand by his call for mass expulsions.