A cross-party commission including the main opposition Republican People's Party (CHP) was set up after a Turkish military faction tried to overthrow President Recep Tayyip Erdogan last July.
The head of the commission Resat Petek said Friday the report "clearly and with certainty" found that the Islamic movement led by Muslim cleric Fethullah Gulen was behind the events of July 15, quoted by state-run news agency Anadolu.
Turkey refers to the movement as the "Fethullah Terrorist Organisation (FETO)".
"All the evidence and documents collected were evaluated together... It was concluded that under the so-called leadership of Fethullah Gulen, FETO decided and conducted (the coup)," Petek said during a press conference in Ankara.
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He added that Gulen had been "supported and protected... for half a century" by forces outside and inside Turkey but did not give further detail.
Gulen vehemently denies the claims and his movement insists it exists to promote Islam, charity and education.
Petek, a ruling Justice and Development Party (AKP) lawmaker, also criticised the intelligence services.
The commission's chairman called for a review, looking at the problematic and inadequate points of the current intelligence structure.
However, Petek said an unidentified soldier from the army's aviation regiment provided information to the head of the spy agency, Hakan Fidan, relating to the coup.
The lawmaker said this was "one of the the most important factors" in the timing of the bid moving forward from July 16 at 3am (0000 GMT) to 8.30pm (1730 GMT) on July 15 because of undefined actions by the spy agency and military chief of staff.
The report will now be given to speaker Ismail Kahraman for final approval in 15 days, Anadolu said.
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