Peretz, who left the Labor Party after the primaries to join Tzipi Livni's Hatnua party, was charged by Labor Party head Shelly Yachimovich of being involved in vote buying in Labor Party primaries.
The primaries are a procedure in which members of the larger political parties choose the party leader and the list of candidates for the Knesset.
Details of the alleged scam involving an unnamed former government minister and a Knesset member of the Labor Party were reported Tuesday by the Hebrew-language daily Yedioth Ahronoth and Ynetnews.com.
Those involved allegedly made payments to "voting contractors," in exchange for votes in the primaries.
Details of the Yedioth report were partially based on an interview with a person identified only as "P," who was said to have a senior position in the Labor Party primaries. "P" was given a polygraph test commissioned by the newspaper, which said the test indicated he was telling the truth.
"We condemn the phenomenon described in the article. We are pleased that those who allegedly committed the acts are no longer members of the Labor Party," a statement issued by Yachimovich and Labor Party Secretary-General Hilik Bar said.
Peretz called the statement "irresponsible," and accused Yachimovich of participating in "blood libels against people," The Jerusalem Post said.
"The details described in the article never occurred and have no connection to reality," Peretz said.
Last week, Yedioth Ahronoth said Israeli police were investigated similar suspicions in the Bayit Hayehudi (Jewish Home) primaries. One of its members, Knesset Member Nissan Smoliansky, was to be questioned under caution concerning the affair, the newspaper said. Smoliansky denied the allegations.