Opposition lawmaker Erel Margalit has urged Attorney General Avichai Mandelblit to open a criminal investigation into Prime Minister Benjamin Netanyahu’s role in a Defense Ministry deal to purchase submarines from a German company partly owned by the Iranian government.

In a letter to Mandelblit on Tuesday, Margalit, from the Zionist Union party, threatened that if a criminal probe into the affair would not be forthcoming, he would turn to the High Court of Justice. A petition with some 15,000 signatures from the public was attached to the letter, Israel Radio reported.

The affair dominated public debate in the country last month, as accusations surfaced that the prime minister may have been swayed in the decision by business ties his personal counsel David Shimron may have had with the submarines’ builder, ThyssenKrupp. The purchase was opposed by parts of the defense establishment, including former defense minister Moshe Ya’alon.

Zionist Union MK Erel Margalit (Flash 90)

Zionist Union MK Erel Margalit (Flash 90)

Mandelblit ordered a preliminary probe late last month into a related affair: allegations that Shimron may have used his connection to Netanyahu in 2014 to lobby for the purchase of ThyssenKrupp ships to protect Israel’s Mediterranean gas fields. Netanyahu himself is not a target of the probe.

Last week, lawmakers tried to force a special debate on the issue in the Knesset Foreign Affairs and Defense Committee, after Iran’s holdings in the German company emerged.

The Defense Ministry has acknowledged that it knew about the Iran Foreign Investment Company’s share in ThyssenKrupp. According to reports in Hebrew-language media, the IFIC has earned nearly $100 million from its shares over the past decade with a 4.5 percent stake.

In a statement to the press last week, MK Tzipi Livni (Zionist Union) listed some of the questions the committee would take up: “Was the Iranian stake in ThyssenKrupp examined before the deal was made, and by whom? Was the issue discussed in the relevant cabinet committee or by sanctions officials? What are the defense ramifications of the partnership of Iran, an enemy state, in the company building Israel’s submarines and naval combat vessels, especially considering the heightened sensitivity and purpose of said submarines? Did the Israeli government ensure — and if so, how — that no information leaked to the Iranian shareholders or the Iranian government, or that the Iranian regime did not benefit from the deal?”

At least some of the deals for Israel to purchase submarines from Thyssenkrupp were made when Livni herself served as foreign minister under Ehud Olmert from 2006 to 2009.