We will never know the full details of the Ben Zygier affair.

It involves secrets having to do with Israeli intelligence and operations - secrets which, if exposed to enemies of the state, could cause Israel tremendous damage. Thus it is unlikely that these secrets will ever be published, as doing so would harm the Mossad's methods even more than they have been already.

The responsibility for this damage falls on the Mossad's people and those who are supposed to supervise them - not on the media, which has operated within the law.

But troubling questions were raised after Israel was forced to officially admit that an Israeli-Australian "security" prisoner had been held in extreme solitary confinement, had outwitted his prison guards and had put an end to his life. These burning questions will not allow the affair to be buried. Answers are demanded, even if not all of them are made public.

It is necessary to launch a thorough investigation to ascertain how a man with questionable personality traits like Zygier was recruited to the Mossad. Has the bar for admission to this sensitive organization been lowered too much in the past decade?

The investigation must look into the Mossad's investigation procedures and its methods for drawing conclusions in order to ensure that errors are corrected. It must also look into the discourse between the Mossad and Shin Bet - and especially their chiefs at the time - to examine whether the Mossad had encouraged the Shin Bet to exert extreme emotional pressure on Zygier, which in turn contributed to his decision to commit suicide.

Also, how did Zygier come to be held under conditions similar to those of the prime minister's murderer? Did the Prison Service have complete control over his fate, or should it have shared this control with the Mossad and Shin Bet? How do the prosecution and courts supervise the enforcement authorities? How much did the supervising outfits know in real time?

The Subcommittee for Intelligence and Secret Services, within the Knesset's Foreign Affairs and Defense Committee, is not the appropriate body to lead such an investigation. In his first term as prime minister, Benjamin Netanyahu survived the Mossad's failed operation to assassinate Khaled Meshal - and the inquiry committee headed by former Foreign Ministry director general Yossi Ciechanover.

The Meshal affair complicated Israel's relations with Jordan. The Zygier affair complicated Israel's relations with Australia. It is vital to probe the latter - as well as the extent of Netanyahu's knowledge of it, and the way his responsibility was implemented - using similar methods.