The PN on Wednesday claimed Transport Malta officials were "personally" orchestrating the berthing of vessels at a Cospicua site in what the party said is the latest in a series of scandals.
PN spokespeople Ivan Castillo, Darren Carabott and Mark Anthony Sammut said in a statement the irregular berthing was being organised off the American University of Malta.
This same university had never updated TM about berthing activities nearby, something it was obliged to do, the PN MPs said.
Instead, berthing was being "orchestrated by individuals on a personal level. These same people are also TM officials featured in other scandals".
In the statement, the PN referred to other "TM scandals", including the agency's buying of defective rigid hull inflatable boats - a procurement that was also slammed by the National Audit Office.
It also made reference to claims that fuel bought by officials for their personal use had been put on TM's tab. TM has denied allegations that two high officials of the agency were under investigation following the theft of fuel.
Thanking "genuine" TM workers, the MPs urged the police and the transport watchdog to say whether three officials had been suspended pending an investigation into the matter.
They also asked whether TM had carried out an internal investigation and whether it would be publishing the findings.
"TM should also make public all activities linked to berthing under the responsibility of TM, as well as TM audits."