The U.S.-based leader of Gülenist Terror Group (FETÖ), Fetullah Gülen, pays a "vast amount of money" for lobbying activities in Washington to "attack Turkey," said Robert Amsterdam, an international lawyer who provides assistance to Turkey regarding the investigation on FETÖ.

"Gülen has spent a vast amount of money on donations to officials. He spends anywhere from half a million to a million dollars a month just on lobbying in Washington," said Amsterdam, adding that Gülen spends money to attack Turkey, and anyone working for Turkey, as well as to promote and protect his activities in the U.S.

Amsterdam & Partners LLP was retained by Turkey to pursue a global investigation into the suspicious activities of Gülen, the mastermind of the July 15, 2016 coup attempt. He has previously documented over $243 million worth of fraud by the group through its charter schools operating in America.

Mentioning "Empire of Deceit: An Investigation of the Gulen School Network," a book published by the law firm in September, Amsterdam said it demonstrates the FETÖ's undertakings.

"The activities of Fetullah Gülen were shielded as in any criminal conspiracy. A tremendous amount of effort is made to shield Gülen," he said.

Amsterdam added that FETÖ schools were run as secret cells of the group. He said that more than 200 schools of Gülen's network operate in the U.S.

The law firm has already initiated a multi-jurisdictional investigation into the terrorist network.