The Prime Minister refuses to comment on claims that the Israeli secret service, Mossad, approached the Security Intelligence Service in a bid to hush up passport fraud involving two men suspected of being Israeli agents.

Eli Cara and Uriel Kelman are serving six months jail for passport fraud.

Two other men are suspected of being implicated in the fraud; one a former Israeli diplomat and the other a former New Zealand ambulance medic.

An Israeli newspaper, Sunday Haaretz, claims Mossad asked its New Zealand counterparts to help cover up the matter but Helen Clark prevented that from happening.

Clark, who is also the minister responsible for the SIS, says she is aware of the speculation but never comments on intelligence matters.

Clark has asked Israel for an apology over the passport fraud but says she has received none.