Prime Minister Joseph Muscat has denied interfering in the police investigation into the murder of Daphne Caruana Galizia, responding to a court case filed by the family on Monday.

On Monday, the Caruana Galizia family filed Constitutional proceedings against the Prime Minister, asking that he desist from further involvement in the investigation into the murder of Daphne Caruana Galizia and place his own involvement in the case under the court's scrutiny. The family had said that the Prime Minister was involving himself in various aspects of the ongoing investigation and "it appears that he has chosen to continue doing so until January 2020 at least."

The Attorney General's Office, on behalf of the Prime Minister filed its response on Tuesday, and said that the developments over the past days in the investigation into the assassination of Daphne Caruana Galizia were important and confirm that the institutions, "in contrast to what has long been said about them, work and do their job well."

The Prime Minister argued that he in no way interfered or is interfering or plans to interfere in the investigation.

The Prime Minister said that he was surprised how "after an agreement with the applicants regarding the change in the composition of the board of the public inquiry regarding the crime, he is being faced with insinuations that he will interfere in the process of the hearing of evidence from that board, and in criminal proceedings."

The letter read that the Prime Minister cannot respond regarding the arrests that could have been made during the police investigations, or what could have led to them, or resulted from the interrogations. He said however, that the arrests that have been made are a confirmation of the independence of the investigations, and not a failure of its independence.

He denied that he is undermining the continuation of the investigation, or is in some way breaching the European Convention of Human Rights.

He asked the family to stop persisting with the allegations and pretentions.