"Even during these days of heightened emotions, such actions of hatred and extremism should be rejected with disgust. The law enforcement system must be firm and alert during these times to prevent serious acts of this kind," a statement issued by the party said.
A suspect, Shvuel Schijveschuurder, allegedly spray-painted "price tag" and "free Yigal Amir" on the Rabin memorial early Friday, The Jerusalem Post reported.
Schijveschuurder lost both parents and three siblings in the 2001 Sbarro attack. An unconfirmed list of prisoners to be traded in exchange for Israeli soldier Gilad Shalit being held by the militant Palestinian group Hamas includes a terrorist involved in the Sbarro bombing.
The Rabin memorial monument officials denounced "all activities of vandalism and damage to the site, which is a symbol and memory of the murder of" Rabin, the Post said.
However, National Union Knesset Member Michael Ben-Ari said the vandal was expressing exasperation felt by terror survivors.
"The release of killers is apt to anarchy and not a lawful state. In anarchy boundaries are crossed, and even Yitzhak Rabin's gravestone has lost its glory and sanctity," Ben-Ari said.