The outcome of the investigation into Daphne Caruana Galizia’s assassination has potentially explosive political ramifications. People at the heart of government, namely Keith Schembri and Konrad Mizzi, are suspected of receiving massive bribes from Yorgen Fenech, who is believed to be a potential mastermind behind Caruana Galizia’s murder.

Fenech was a director of Electrogas, the company that won a hugely lucrative tender to supply Malta with electricity, a process in which Schembri and Mizzi were deeply involved. Caruana Galizia’s cryptic posts about Fenech’s company 17 Black, later revealed by a leaked email to be behind payments of millions intended for Schembri and Mizzi’s secret Panama companies, came at a sensitive time for Electrogas as it was still setting up its operations.

The moral imperative is now stronger than ever for Schembri and Mizzi to be sacked. This should have been done as soon as their offshore companies were revealed. These are normally used to evade financial and tax regulators. The pair’s link with Fenech – ­even if he has still not been charged – now makes the Prime Minister’s continued failure to take action against them utterly indefensible both politically and morally.

As events surrounding the investigation proceed at a breathtaking pace, the Prime Minister has taken centre stage. He – instead of the police – has been the one briefing the press about a potential pardon for the apprehended middleman, about the interception, arrest and bailing of Fenech. Once again, the police have been totally absent in the vital function of fulfilling the people’s right to know.

More worryingly, Muscat is clearly in a powerful decision-making role in this affair. He is part of the negotiations on the pardon, he has admitted to boosting resources that made possible the apprehension of Fenech, and he admits to long having known certain undisclosed facts.

This constitutes a massive conflict of interest. His closeness with Schembri means that he is tainted by association with any new allegations that could be made against the chief of staff. We cannot be sure whether Schembri is also influencing the direction of the investigation.

Muscat is a major player in a probe whose outcome will have make-or-break implications for his political future and beyond. What does he know? For how long has he known it? These are among the legitimate questions that any objective citizen would be asking.

The Prime Minister on Friday reiterated he was not sheltering anyone. This is not enough. His shielding of Schembri and Mizzi for the last two years strongly repudiates that assertion. It is just too late for him to deny that he is protecting anyone and expect to be trusted.

It is critically important that he steps away from any involvement in the investigation, whether fronting it or making decisions that have a bearing on its progress. He must, in effect, recuse himself, hand over any prerogative to his deputy and allow investigators to work in total independence.

Even beyond the risk that the Prime Minister could be influencing the probe, the country badly needs closure on this terribly divisive episode. Closure can only come if it is accompanied by certainty: the certainty that, when justice is finally done, it rests on a solid basis of truth. No shadow of doubt must remain. Otherwise, the deep wound inflicted by the murder will fester on.