US regulators are reviewing the consent decree that allowed Macquarie Group Ltd to purchase Advantage rental brand from Hertz Global Holdings. The approval of the acquisition by the private equity firm is still pending from antitrust regulators.

The bid amounted to US$2.56 billion for Dollar Thrifty Automotive and the review by the Federal Trade Commission is based on the shrinkage of car rental chains from four to just three firms. One of the requisites for the review is that Hertz sell off locations in order to recreate a fourth competing firm after the absorption of Dollar Thrifty.

Hertz sold off its Advantage brand last November 15, 2012 and was the only direct competitor of Dollar Thrifty in the low end segment of the market. The purchasers were Franchise Services of North America and Macquarie Capital. 

The FTC could not be reached for comment by Reuters beyond regular office hours. Macquarie Capital also declined to comment.