Ari Harow has been named as the senior former member of the Prime Minister's Office (PMO) being investigated on warning, amid suspicions of breach of confidence and receiving benefits through fraud.
The American-born Harow was investigated by police for several long hours on Monday, and then released to a five-day house arrest.
The former official served under Prime Minister Binyamin Netanyahu as the chief of personnel at his office.
He is suspected of acting in a conflict of interests, apparently using his position to advance a company that he owned at the time, in addition to other suspected offenses.
According to the suspicions against him, Harow committed the abuse of office over a long period of time during his service, as opposed to a single isolated incident.
After working in the PMO, Harow early this year moved on to the Likud election headquarters.
In early October, it was revealed that Netanyahu's adviser on Knesset affairs Perah Lerner had been put under investigation for suspicions of fraud, breach of trust, and other offenses.
According to the suspicions against her, Lerner gathered internal information that she came across in her role as Netanyahu's adviser, and passed it to her husband, public relations executive Avi Lerner. The information is suspected to have helped him in several projects and campaigns that he managed.