Confirmation by the Office of the Prime Minister that Joseph Muscat continued to exchange SMS messages with Yorgen Fenech, the alleged mastermind of the Daphne Caruana Galizia murder, reinforced the need for Dr Muscat to leave office immediately, the Nationalist Party said on Wednesday.

The Office of the Prime Minister, reacting to media reports, confirmed earlier that Dr Muscat had exchanged messages with Mr Fenech, but said he had done so in agreement with the Security Service so as not to alert Mr Fenech that something was amiss.

The PN said Dr Muscat had been communicating with Mr Fenech when he knew that he was the suspected plot mastermind. He also knew he was the owner of 17 Black, the secret company named as the vehicle to channel funds to the Panama companies set up for then chief of staff Keith Schembri and minister Konrad Mizzi. 

"The exchanges confirm how close Joseph Muscat was to alleged criminals," the party said. 

Mr Muscat also used to let Mr Schembri attend Security Service meetings, giving him access to sensitive information, the party observed. 

"The prime minister has no choice other than to leave office immediately, to stop causing irreparable harm to the country. His position is untenable and the country cannot stand seeing its reputation further undermined," the party said.