Prime Minister Binyamin Netanyahu took a harsher line than he had previously taken against revelations that the US National Security Agency (NSA) had spied on Israeli leaders, saying Monday that their were some things which were "unacceptable" among allies.The only statement that the prime minister had made previously regarding US spying on former prime ministers Ehud Olmert and Ehud Barak was to give vague reassurances about regular Israeli efforts to release Jonathan Pollard from US custody, reacting to the spin-off story about how these revelations should impact his fate.However on Monday, speaking at the weekly Likud faction meeting, Netanyahu said that he had asked the US for "clarifications" on the matter. "In the close relationship between Israel and the United States, there are things which are forbidden to do, that are unacceptable to us," the prime minister said.Netanyahu again brought up Pollard in relation to the NSA spying allegations, telling his faction that he met Monday with the Israeli agent's wife, Esther."I met now with Esther Pollard and updated her on the nonstop efforts to win Jonathan's release. He should have been released long ago. I think this is understood by everyone here and I believe it is also understood to an increasingly larger crowd in the United States," Netanyahu said.The revelations of NSA espionage that appeared in The New York Times Friday were based on documents former NSA contractor Edward Snowden leaked.According to the report, in January 2009, spies monitored the email traffic of Olmert in the waning days of his tenure. The next month, Ehud Barak’s email traffic was intercepted.