The Ukip leader, Gerard Batten, is facing calls to be stripped of his European parliament allowance for a month over “inflammatory” language in the Brussels chamber.

A Scottish National party MEP, Alyn Smith, has written to the European parliament president, Antonio Tajani, calling for sanctions after Batten accused British politicians of being “traitors, quislings and collaborators” in a speech that also compared EU leaders to Adolf Hitler.

In a letter to Tajani, the Scottish MEP said the European parliament’s rules needed to be tightened up to prevent abuse by those who, he argued, misled the public with “a drip, drip, drip of the worst sort of misinformation”.

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“It is clear that many UK MEPs have used the platform and visibility this house affords them to at best propagate a misleading and skewed impression of the EU and all its works, and at worst to spread language tantamount to hate speech,” Smith wrote. “These are not isolated incidents, they are deliberate and sophisticated campaign to undermine our democracy.”

Batten benefits from an arrangement with Marine Le Pen’s far-right group, the Europe of Freedom and Nations. He and two Ukip MEPs joined the far-right group in January after falling out with their former leader Nigel Farage over the direction of the party. Batten has become the Brexit spokesman for the ENF, which guarantees him a speaking slot in debates with EU leaders.

Farage quit Ukip in December but continues to lead another Eurosceptic group in the parliament, the Europe of Freedom and Direct Democracy, a position that affords him prestigious speaking slots.

As Ukip leader, Farage was among the first to realise the potential of the European parliament’s web-streaming service. Other Ukip MEPs have taken lessons from Farage, whose short speeches on the floor of the parliament attacking the project and mocking EU leaders found a much bigger audience on social media.

Batten, in his speech, took up his familiar narrative of Brexit “betrayal”. Addressing the European commission president, Jean-Claude Juncker, and the chief Brexit negotiator, Michel Barnier, he said: “You have done what Philip of Spain, what Napoleon, what Kaiser Wilhelm and Hitler couldn’t do. You have brought Britain to its knees without firing a single shot. But you could not have done any of these things without the connivance of the traitors, quislings and collaborators in the British parliament and the British establishment.”

Following his speech, Smith raised a point of order with the European parliament vice-president Mairead McGuinness, who was presiding over the session. She promised to raise the issue with Tajani and said she had been concerned by the phrase “punishment beatings”.

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The European parliament’s rules of conduct require MEPs to act with “mutual respect” and not use offensive language. Breaking the rules can result in members being issued with a formal reprimand, losing the €320-a-day subsistence allowance for up to 30 days, or being stripped of the right to attend committees and overseas trips.

Following criticism of his speech, Batten wrote on Twitter that he was not “ridiculing Juncker or Barnier [but] recognising their achievement”.