The Nationalist Party has said it is "shocking" to see state institutions not react after a state witness implicated former minister Chris Cardona in a plot to murder Daphne Caruana Galizia. 

Hitman Vince Muscat told a court on Wednesday that he drove George Degiorgio to Portomaso to meet Cardona in 2014 to discuss a €150,000 hit on Caruana Galizia.

"I took him [Degiorgio] to Portomaso and dropped him off at the roundabout," he said, adding that later Degiorgio told him that the meeting was about settling the sum to "get rid" of Caruana Galizia. Cardona has always denied any involvement in the murder. 

Both Muscat and Degiorio were convicted of murdering Caruana Galizia in a separate plot three years later. Muscat is serving a reduced sentence in return for information. He gave evidence in court action for damages instituted by the Caruana Galizia family.  

"The silence and inaction confirm that under Prime Minister Robert Abela, the culture of impunity created by Joseph Muscat continues to reign," the PN said.

It insisted that impunity be replaced by a culture of truth and justice and that the government stop interfering in the workings of the institutions. It also needed to ensure that the recommendations made in the Daphne Caruana Galizia inquiry were implemented.

Only in that way could the truth be known about politicians such as Joseph Muscat, Keith Schembri, Chris Cardona and Konrad Mizzi.

The PN statement was signed by Karol Aquilina, shadow minister for justice.