Giuseppe Conte, Italy’s prime minister broke away from a conference that will bring together anti-gay, anti-feminist and anti-abortion and pro-conversion therapy activists from around the world in Verona after organisers seemed to suggest his office had supported the event.

The logo of the Italian prime minister’s executive office had been used without his approval to promote the US-run World Congress of Families event, which aims to return the “natural order” and has widespread reinforcement from Italy’s far-right League party.

Use of the logo to promote the three-day event, which takes place at the end of this month from March 29 to 31, was agreed by the families minister, Lorenzo Fontana, a League politician from Verona who previously said gay marriage threatened to “wipe out our community and traditions”.

Vincenzo Spadafora, a Five Star Movement (M5S) parliamentarian with responsibility for equal opportunities, told La Repubblica:

“The secretary general of the prime minister’s office completed a very important investigation and has asked the ministry of families to remove the patronage. I was among the first to highlight the problem.”

Italy is holding the Congress, which is expected to be attended by Matteo Salvini, the co-deputy prime minister, and leader of the League, amid mounting opposition from rights’ groups and the party’s coalition partner, M5S.

Luigi Di Maio, the M5S leader, and the co-deputy prime minister said on Wednesday that the conference was for “right-wing losers” and that League politicians attending did not represent the government but their own political ideals. Marco Bussetti, the education minister, was also scheduled to attend.

The international guest list includes Theresa Okafor, a Nigerian activist who compared gay people to the Boko Haram terrorist group, and Lucy Akello, who supported a law in Uganda mandating the death penalty or life imprisonment for gay people. It will also be attended by Katalin Novák, the Hungarian minister for family affairs, and Konrad Głębocki, Poland’s ambassador to Italy.

The event’s website described the Congress “as one of the greatest international initiatives that affirm and defends the natural family as a fundamental unit of society”, and said organisers expected thousands to descend on the city which was a model for “pro-life”.

While rights’ groups welcomed the removal of the patronage, Fabrizio Marrazzo, a spokesperson for the Rome-based Gay Centre, said he was “flabbergasted” by the support of League ministers. “The respect of human rights should be a priority for government exponents, and such ministers should renounce their presence at the Congress,” he said.

Alessia Rotta, a parliamentarian with the opposition Democratic party, said the government’s goal ought to be “radically changing the culture” in a country with one of the highest rates of femicide in Europe and which has serious problems with sexism and homophobia.