The comments came after a major rally took place in Milan on Saturday to defend the rights of same-sex-parent families.
The protest was organised after Milan was forced to stop a procedure it had used to register both members of a same-sex couple as the parents of a child.
The prefect's department warned the course of action was illegal following consultations with the interior ministry.
It 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 in that country.
"If two people of the same sex request that a child they are passing off as theirs be registered in the civic register, it means that they have done surrogacy outside the national borders," Rampelli told La7 television late on Saturday.
Pina Picierno of the opposition, centre-left Democratic Party (PD) said Rampelli's comments were "nasty".
"Violent reactionaries are passing themselves of as politicians worthy of the country's government," Picierno added.
Equal Opportunities and Family Minister Eugenia Roccella said it was false to argue that the children of same-sex parents were getting second-tier treatment.
"There is no denial of children's rights," Roccella told Rai television.
"They all have the same rights in Italy".
She added that, while she did not agree with the words Rampelli had used, the concept was correct.
"You have to declare a series of things at the civil registry and, if you say that two fathers are both the parents, you are saying something that is not true," Roccella said, adding that she considered surrogacy to be a "market of children".
ANSA
