The former Conservative minister Ann Widdecombe has likened the UK’s departure from the EU to the emancipation of slaves, as she became the first Brexit party MEP to speak in the new European parliament.

With her leader, Nigel Farage, on her right, Widdecombe said the recent negotiations among the EU’s heads of state and government over the leadership of the bloc’s institutions confirmed the need for Britain to leave.

“It’s not democratic at all and that is just one of many reasons why Britain is right to be leaving this place, hopefully on Halloween,” Widdecombe told a plenary session of the European parliament in Strasbourg. “If that’s this place’s idea of democracy that’s a serious betrayal of every country represented here.”

Widdecombe, who was criticised this month for claiming science might “produce an answer” to being gay, said the UK’s departure from the EU equated to a liberation.

She said: “There is a pattern consistent throughout history of oppressed people turning on their oppressors, slaves against their owners, the peasantry against the feudal barons, colonies against empires, and that is why Britain is leaving … It doesn’t matter which language you use, we are leaving and we are pleased to be going. Nous allons [sic], wir gehen, we are off!”

The Brexit party’s MEP for the South East, Alexandra Phillips, tweeted: “Tears in my eyes. She represents the ignored majority. Brave and principled. Our Ann.”

Germany’s defence minister, Ursula von der Leyen, 60, was nominated on Tuesday by leaders including Theresa May to replace Jean-Claude Juncker as the next European commission president but she will only take up the role if a majority of MEPs vote in favour of her candidacy.

Theresa May’s spokeswoman said the prime minister did not agree with the comparison: “That isn’t a characterisation she would recognise, nor is it a phrase that she would ever use to describe leaving the European Union.”

Guy Verhofstadt, the Brexit coordinator for the parliament, expressed his scorn at Widdecombe’s comments.

“Nigel Farage facing some stiff competition as chief clown of the Brexit Party in the [European parliament],” he tweeted. “By the way, when Widdecombe talks about ‘colonies liberating themselves from their empires’, is she really referring to the American Revolution of 1776?”

The Liberal Democrat MEP Martin Horwood, who also took part in the debate, said: “To imply that the United Kingdom is any way in a similar situation to the colonies of our former empire or a victim of slavery is deeply offensive. Widdecombe’s comments trivialise the suffering of those who have experienced slavery and colonialism.

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“If Ann Widdecombe had any grip on reality, she would have the sense to look at her own record on oppressing women and minorities when she defended shackling pregnant women and opposed repealing section 28.

“Ann Widdecombe has not only embarrassed herself, but she has embarrassed the nation she represents. I hope she withdraws her comments and sincerely apologises to all those she has offended immediately.”

This week Brexit party MEPs faced criticism for turning their backs when Beethoven’s Ode to Joy, the EU anthem, was played in the chamber on the opening day of the five-year term.

Widdecombe’s comments followed a speech by Donald Tusk, the president of the European council, who asked parliament to back the leaders’ nomination of Von der Leyen in the commission and of Christine Lagarde as president of the European Central Bank, breaking more than 60 years of male monopoly of the leadership of the institutions.

Q&A What does the European commission president do? Show Hide The president is proposed by the European parliament and nominated by the European council of leaders of the EU member states. They lead the commission's work in implementing EU policies, chair the weekly commission meetings and set its policy agenda. They also represent the EU at European council meetings, G7 and G20 summits and at bilateral summits with third countries. The role was held by Jean-Claude Juncker from November 2014 until July 2019, when he was replaced by Ursula von der Leyen, the former German defence minister. Photograph: Jean-François Badias/AP

“This is a very positive change,” Tusk said. “Europe is not only talking about women, it is choosing women. I hope that this choice will inspire many girls and women to fight for their beliefs and passions. And I also hope that it will inspire the European parliament in its decisions.”