"A clearer law is needed," Bologna's centre-left Mayor Matteo Lepore said, referring to the supreme court ruling that the government has used to stop mayors registering the children of gay couples, but which appears to be open to interpretation.
Several hundred people defied steady rain to attend the Bologna rally, held in the iconic central Piazza Maggiore.
The mayor of the northwestern port city of Savona, Marco Russo, on Saturday became the latest local official to have flouted the government ban and register the son of two women.
The child, conceived in Barcelona with the assisted fertility of one of the women, was born in Savona last week.
It was the first case of registration of the child of a same-sex couple in Liguria since the government stopped the practice.
Russo explained his decision to prosecutors and the prefect saying that he had signed the act personally without involving any other functionaries.
"I challenge the ban, the government is far away from reality", he said.
The European Parliament last Thursday approved an amendment to its motion for a resolution on the rule of law condemning "the instructions given by the Italian government to the municipality of Milan to suspend the registration of adoptions of same-sex couples".
The amendment was submitted by the Renew Europe group and supported by the Left, Greens and Socialists.
Milan was recently forced to stop a procedure it had used to register both members of a same-sex couple as the parents of a child after the prefect's department warned it was illegal following consultations with the interior ministry.
The procedure was based on the transcription into the Milan civil register of foreign birth certificates of children conceived by surrogacy, which is illegal in Italy, or assisted fertility, which is only allowed for heterosexual couples here.
Furthermore, Premier Giorgia Meloni's right-wing Brothers of Italy (FdI) party has tabled a bill that would make surrogacy a "universal crime", meaning that Italians could be prosecuted for using the practice in foreign States where it is legal.
Many Italian same-sex couples have had children via surrogacy outside the country.
The centre-left Democratic Party (PD) has condemned the government's actions and said it will fight to pass legislation protecting the rights of same-sex-parent families.
Milan Mayor Beppe Sala last Wednesday called for all the opposition parties to form a broad alliance to fight for the rights of same-sex-parent families.
On Sunday he accused the government of "trying to take us back into the past".
Foreign Minister Antonio Tajani on Friday stressed the government's opposition to surrogacy amid the row on registering same-sex couple's children in Italy saying that women's bodies weren't like ovens that bake potatoes.
"A woman cannot be exploited: she is not a cigarette machine,"Tajani, who is also deputy premier and Silvio Berlusconi's deputy of the centre right Forza Italia (FI) party, said on the sidelines of a local election rally in the northern city of Udine, after the European Parliament came out for the rights of same-sex families and their children.
"A woman's womb must not be used to churn out children as if it were an oven where roast potatoes are baked," he said.
ANSA
