Davutoglu has followed the lead of President Tayyip Erdogan in dismissing the graft scandal, which erupted in December 2013, as an attempt by political enemies to topple the government.
The commission, dominated by members of the ruling AK Party, voted on Monday not to commit the four ex-ministers for trial, a decision that the opposition decried as a cover-up of one of the Turkey's biggest ever corruption scandals.
Speaking at a weekly parliamentary meeting of the AK Party, Davutoglu said it would be against the law for the government to impose a decision on the commission. He cast a string of turbulent events, including nationwide anti-government demonstrations in 2013 and a wiretapping scandal last year, as part of a wider plot.
"Regardless of the commission's decision ... it was all, without doubt, a coup attempt and we have stood tall against this," he told AK Party MPs and supporters in a speech regularly interrupted by cheering.
The scandal swirled around the inner circle of then-prime minister Erdogan and led to the resignation of the ministers of the economy, the interior and urbanisation. European Union Affairs Minister Egemen Bagis lost his post in a subsequent reshuffle. All four have denied wrongdoing.
The parliamentary commission was set up last May to decide whether the men's ministerial immunity should be lifted.
All nine AK Party MPs were against, and all five opposition members in favour. A final decision will be taken in a full session of parliament, where the AK holds a large majority.
The commission's decision effectively backed Erdogan's efforts to stamp out the scandal, which he blames on supporters of his former ally, US-based cleric Fethullah Gulen.
The government has reacted with a purge of the state apparatus, reassigning thousands of police and hundreds of judges and prosecutors deemed loyal to Gulen, in what the authorities said was a cleansing of the cleric's influence.
Turkey's Western allies have repeatedly called for a transparent investigation into the allegations and have expressed alarm at what they see as creeping authoritarianism. Erdogan has responded by telling Turkey's European partners to "keep their wisdom to themselves".