Emanuele Pozzolo, a lawmaker for Meloni's far-right Brothers of Italy party, has admitted owning the mini revolver but says he did not fire it.

A guest was shot in the thigh, although not seriously injured, in an incident that prompted criticism from opposition politicians and making news across the world.

At her traditional end-of-year press conference, postponed from December after she fell ill, Meloni failed to hide her frustration at the incident.

She said she did not know all the facts, but said that "someone was not being responsible and the person who was not responsible was... the owner of the gun".

Meloni said she had asked the case be referred to a party commission and "pending a decision, he (Pozzolo) be suspended from Brothers of Italy".

Such a situation was not acceptable for any Italian, "let alone for a parliamentarian, let alone for a Brothers of Italy lawmaker", she said.

"On this I intend to be strict, as you can see."

Prosecutors have launched an investigation into the incident, looking into possible offences including involuntary or negligent injury and failure to safeguard a weapon.

They said in a statement they have also seized the gun, a North American Arms 0.22 handgun, and the bullet.

The victim is reported to be the son-in-law of a bodyguard of junior justice minister Andrea Delmastro, whom newspapers said also attended the party in Rosazza, near Turin.

Pozzolo, 38, said in a statement earlier this week that "the shot was accidentally fired from a pistol I legally owned but it was not me that fired".

Possession of firearms in Italy is strictly regulated, although Meloni's party last month proposed to reduce to 16 the minimum age for obtaining a permit for a hunting rifle.

Opposition politicians expressed astonishment at the incident and had asked for Meloni to take action.