The Italian prime minister has distanced himself from a conference that will bring together anti-gay, anti-feminist and anti-abortion activists from around the world in Verona, after organisers appeared to suggest his office had endorsed the event.

The logo of Giuseppe Conte’s administrative office had been used without his endorsement to promote the US-run World Congress of Families event, which calls for a return to the “natural order” and has widespread backing 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, was agreed by the families minister, Lorenzo Fontana, a League politician from Verona who once said gay marriage threatened to “wipe out our community and traditions”.

The families ministry has been told to remove the logo from the event’s website, with officials voicing anger that it was used at all.

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 hosting 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 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.

Salvini said in October he was proud that Verona, a staunchly Catholic city where the council introduced a motion to fund anti-abortion groups, was playing host. “This is the kind of Europe we like,” he said.

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 affirms 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.

Protesters were expected to rally at the event from 29 to 31 March.